Bristol_Jonesey
Zargg71
Boydie
If I am mastering my own mixes (or mixes I have made from raw tracks submitted by clients) I will do my mastering within the project on the "master bus" so that if required I can go back to the original mix and tweak anything "on the fly" rather than trying to "fix it" in the mastering
This is how I usually do it myself.
All the best.
Likewise 
I'm going to fly the flag for
not doing it this way. Just a personal view, of course, but here's my argument.
The longer you listen, the more things to change you will find. And there is no upper bound on this. You can literally go for as long as mortality allows.
Maybe the hi-hat could be louder. Maybe the bass could be more prominent. Maybe the thing on the left could go on the right. Will any of this have any impact on how much it connects with an audience? Well, after a certain point, no.
All the real value of a mix, I think, happens in the first few hours. After that, you're just prevaricating. And possibly even making things worse.
I like to get the mix so it's exciting, and then either master it, or hand it over to someone else to master, and mark it DONE. If, during the mastering process, I think, "hmm, maybe we could have had the shaker 1/3dB louder", my default decision is "ah well, who cares". Very occasionally, there'll be something that makes me think, "no, really need to go back to the mix on this". This is
extremely rare.
None of that's because I'm a god-like mixing wizard; I'm not. But I do know a lot about one thing, which is
how to finish stuff. And a good way to finish stuff is to not keep giving yourself easy back-doors and room to lose both your original vision and your nerve. If the current record has a flaw, make note, and resolve to do better on the next one.
I think that's key to two things that I'm guessing we all want: both to get stuff done, and to
get better at doing stuff. And I've seen this many times: someone who has spent years working on music, has started a hundred things, and finished none.
I really believe it's good to learn how to live with your decisions. Nothing will ever be perfect. You will never be 100% happy. Something will always niggle at you. That, right there, is the price of creativity.
So while people are saying you
can blur the line between mixing and mastering, well, sure. You
can. You can, alternately, build a massive wall between the two, with heavy security and unleashed attack dogs. I think the latter tends to be far more productive.