Left my focusrite Isa one on for a week

I routinely left my old MOTU on for literally weeks at a time, sometimes months. It lasted for years. Right up until the day it died at the ripe old age of 7.
 
Fearing I'd shortened its life by turning it off so infrequently, I now make a point of powering down its replacement when I shut down at night. Probably for nothing, though. In reality, turning it on probably stresses it more than leaving it on (ever notice how light bulbs fail just as you turn them on?).
 
Assuming it wasn't crazy hot that week, any piece of solid-state electronic gear that can't handle being on for a week is garbage, and Focusrite stuff ain't garbage.

I don't think it will hurt it, unless it was overheated.  If it was overheated and actually caused some type of problem usually those don't show up until later.  I have an ISA One and I've left it on for two days, by mistake, one time and it didn't (apparently) hurt it. 
 
 

I agree with storing mics for safe keeping.
 
Except for monitors, I leave all my gear on 24/7/365. Like bitflipper was saying, I tend to think the initial current rush is part of the cause of electronic failures but also the heat/cool cycles. I think the insulation (like shellac) on transformers and chokes and the various capacitor materials tend to age quicker with heating and cooling (expansion and contraction)
 
I may spend more on electricity in the long run but I think I save time by not having to recover from as many failures. Either way, "The world may never know."

+ 1 to the KIll a watt meter and others like it. My Daughter was living off the grid for a few years and bought one so they could see what was hogging power.
Our studio's use very little power. 
I'll ask her if she still has it and run it on mine. 
I also have an old freezer someone gave me that never shuts off much,,, I want to test that pig.. might be worth it to buy a new more efficient model. 

DrLumen
I agree with storing mics for safe keeping.
 
Except for monitors, I leave all my gear on 24/7/365. Like bitflipper was saying, I tend to think the initial current rush is part of the cause of electronic failures but also the heat/cool cycles. I think the insulation (like shellac) on transformers and chokes and the various capacitor materials tend to age quicker with heating and cooling (expansion and contraction)
 
I may spend more on electricity in the long run but I think I save time by not having to recover from as many failures. Either way, "The world may never know."

On the other side of the coin I dont agree. I have been turning my studio on and off now for 37 years! Not one failure due to this approach either so how do you explain that! Except I do do it in a sequence though. Not everything at once. Leaving gear on is a myth. (Older gear yes but not these days) Especially computers. Windows does not like being on for a long periods of time. It is well known that you should cold boot your computer.  Leaving your gear on also consumes a lot of power over a year.  Electricity is getting far too expensive to do it these days. Leaving your  computer on even in standby is running the power supply as well. Basically you are wearing it out faster, much faster.
 
And if you go away for three weeks and leave you gear on then you are even more silly. You are leaving yourself open to some real potential problems due to storms etc.. Lightening strikes etc..You need to totally disconnect power when you go away. 
 
I used to teach sound engineering in a school that had an old Harrison M32C console and yes that had to stay on for sure.  It just did not like being turned on and off.  It drew over 1KW permanently and the power supply got so hot it had to be in a room of its own with an air con permanently aimed at it in order to keep the temp under control. But a lot of modern gear these days e.g. digital mixers don't have to operate this way.

I have encountered the odd situation in Windows where it was doing something strange.  Restarting did not cure the problem.  Only turning off completely waiting minute and doing a cold boot did the problem disappear.  This is with current systems.  It still happens today.  Not as often I agree bit still can happen.
 
People who leave their computers on permanently will put up with a situation like that and probably waste quite a lot of time trying to rectifying it as well.  Not even thinking that a complete turn off and a cold boot would fix it.  It happened to konradh recently in the Sonar threads.  
 
 

With microphones yes the best approach is to definitely keep them packed up.  And if they do have to stay out overnight or for a few days due to a long session a good thing to do is to cover them with a small open ended bag of some kind. Note, open ended is important otherwise moisture could build up.  The worst thing that may have happened in the OP's case is the diaphragm being exposed for week while charged to airborne dust.  But if there was no one around at least for a week the amount of airborne dust would have been minimal.  I am sure your microphone is fine.  Your preamp will also be fine too.  Please don't be tempted to clean the diaphragm or even apply any air dusting to it etc.. It is very delicate and can be damaged permanently very easily.  Just keep it stored in between uses safely. 
 
I agree with Daniel re turning gear on and off I think these days with gear drawing so little power now too and being able to immediately offer identical performance as well the moment it is switched on.
 
Like I mentioned with the Harrison console and also with me in the 80's with a lot of vintage analog synths they did not mind being powered up but they did often take a while to warm up and get back to the sounds they had previously or in most cases they never actually returned to their previous sounds anyway.  I used to leave some stuff on if I was very tired and not able to track a part say.  I would leave them on and then next morning get up and do it.   With digital synths now of course this is not an issue anymore as they do power perfectly to the same sounds they had previously.  The argument for leaving your studio on is weak now. 
 
There is also an argument against leaving stuff on too.  With the Harrison console we were in an area that was prone to voltage fluctuations and spikes and the disadvantage was although the console would be very stable due to being left on, sometimes it used to take a power spike in the middle of the night and then we had to get the power supply repaired which was usually very very costly. We had to carry a spare because of this.  In the end we had to get a special UPS that totally isolated the console. But it cost a fortune because the console drew well over 1KW and the cost of a UPS that can handle that sort of power starts to get very serious. 

Now, because I've said something....if my PC or laptop doesn't boot up tonight I'll be upset.....

A side note...I've had my Edirol FA 101 on for the last 5 years except for hurricanes. No reason, just where it sits on my desk.