1) what is the best time to buy UAD cards ? UAd Plugins ?
UA does offer promotions, there doesn't seem to be any set schedule. Right now you can get a satellite free if you buy and Apollo 8, 8p or 16.
2) Can i use a friends vouchers (from its account ?)
I don't think so, I'm pretty sure they are tied to the user and/or system.
3) How do you find the system ? stable ? well maintained for windows ? Support ?
I've had a UAD card since they were distributed by Mackie, I can recall only one occasion when the card caused problems, I'm pretty sure it was after a firmware update, but I don't recall the details, and it was quickly resolved. So stability is not an issue.
Well enough maintained for Windows. And most of my gripes on that front have more to do with MS than UA.
Support is outstanding, although I haven't had a tech support issue in years. When I first purchased my UAD2 card I had some minor struggles getting my computer to recognize it. Turned out to be an arcane issue with my motherboard, and changing slots solved it. They were able to talk me through it on the phone, and even checked in a few days later, via email, to make sure it was still working.
The user community is also remarkable. Very knowledgeable, very helpful, and you'll run into names you may have seen on record jackets, but they'll never tell you<G>!
4) anybody tried Thunderbolt to usb C or usb 3 to usb C adapter with success ? if so , witch model/brand ?
I'm stuck at the moment, my computer does not support TB, so for me to make the leap requires a new computer and a new Apollo, and I just can't justify the cost. I'll get there, but not right now.
5) If possible to go back in time , would you have done the same choice or been going native instead ?
Absolutely. There are plugins that simply do not exist anywhere else (Ocean Way Studios, Cooper Time Cube), there are plugins that exist elsewhere, but it is nice to be able to off-load the processing when I need to (Softube, Brainworx), and then there are the plugins that are just spot on accurate representations of what I think gear should sound like, like their own 1176, or the dBx 160, or the tape delays.
TL;DR - for emulations I think the UA plugins are, in general, as good as it gets. I do wish they'd stretch a little bit more, but they are my go to tools for hardware emulation. Others can come close, sometimes really close, but I use UA most of the time because it takes some of the workload off my CPU. And the cards act as a dongle of sorts, so there is less fear that they'll be hit by piracy.
They are not cheap, but I think it is worth it.