It will be fine. I have about 35 hours of work done so far(arms and back mostly). Most tattoos won't need a touch up for at least 15 years or more, but I really think people worrying about touch ups is a bit over exaggerated. Yes color will fade(personally avoid color), but it's not like the tattoo will be a blob.
Plus do you understand what will be done with a touch up? its not so much brighting areas, this doesn't work because fresh ink looks much different then older ink. They will need to recolor/shade every area, more or less redoing the whole tattoo.
As for the area you want. The upper back is a pretty solid choice for longevity. It doesn't see the sun a lot and even with squats it gets relatively little wear. There are some areas to avoid if you a worried about this but the back isn't one of them.
Biggest thing I can suggest for getting a tattoo that will stand the test of time, is make sure the tattoo isn't full of small detail. Small detail doesn't last. Take a look at whatever you want, and either avoid small detail or make it large enough that the smallest detail isn't tiny.
It will look good for a few years but as time goes on that minute detail will fall apart. There is no way to touch up this fine detail that will make it pop again.