I've been dealing with DAWs for several years in my typical hack/non-traditional style. it's true, for serious use, you don't really want to update anything once you have a rig that is working. But I think this is becoming less and less true, but still, better to be on the safe side. I think it is more true for the high end tools and software than for the hobbyist, which is where i seem to have evolved to. for example, if you have a windows or mac machine, and are running cubase, pro tools, logic, etc. i would be very cautious about updating and stuff, because those things are VERY sensitive setups. i had a cubase setup that i eventually updated and the tracks and everything just won't play anymore. i can probably fix it, but it would be a headache.
now, i've moved to reaper on windows 7, which is a setup i have fallen in love with big time. reaper is practically free ($60 for home use, and will work unregistered forever so basically free). reaper is a tiny installation (8 mb) which is mind blowing when you consider the sizes of the professional software, which i have no desire to use again. it is kept up to date, and very flexible with it's file management and importing/exporting stuff. this is a big deal because the other companies are not, and that is often what makes changing things so hard in the future. anyway, i'm a huge fan of reaper, it's something very special. and i'm still a beginner. it's been rock solid and has been able to do anything i have come up with.
i like windows 7 for daw, haven't tried win 8, probably won't for a while. windows 7 has been no problem so far. one thing i recommend for daw...SSD. especially if you work with samples, but even if you don't. SSD's are perfect for music production, has made the biggest difference of anything else i've noticed.
i see that you are concerned with time-machine like saving of files. I don't really relate, but i understand. Most of these daw software have pretty good undo/redo capabilities, so that's good. but if you save a file and overwrite it and want to go back from the one a week ago...i guess that's difficult. i want to say don't worry too much about that, but don't want to dismiss it outright. here's the thing...i don't think it would work all that well anyway, trying to go back and recover stuff like that. you can use something like autover to monitor the folder and keep backup versions of the file everytime you save it again. i do that for word docs, but not for music. i find it's just better to do it manually. for example, if i have a good track recorded, but i want to experiment with a new setting or something that i'm nervous about, i'll do a "save as" and start with a different file, just for insurance. trying to automate that pschology/behavior will probably not work as well as your thinking. you just know when you are making a big change and you should be aware of it.
i know it's a bit of a rambling, but in conclusions:
win7 64 bit, SSD, reaper, lots of RAM, avoid external drives (especially usb), get a good soundcard (M-audio at least). this is my advice.