The 717 is one of the best built Sansui integrated of its time dual mono internal design etc. very robust build. that said the whole "if it isn’t broken don’t touch it" thing is so very wrong in a whole lot of ways. you would not get on an airplane that had maintenance plan like that would you? obviously, an integrated amp is not an airplane, but all things degrade over time. so, get it checked.
I highly recommend getting it serviced specially if it’s never been in before. one, the bias is going to be way off by now, the caps are getting very old and have drifted out of spec most likely if not already starting to fail. the list goes on.
The 717 is highly regarded on the use market as well and commands top dollar if in good shape, and the prices are only going up as more people see how good these Sansui’s were.
If it was mine, I’d have it restored and brought up to factory spec you will be surprised how much better it will sound after a refresh.
I’ve done all my Sansui vintage stuff now and everyone was better after a refresh. I’ve done an; AU 20000, CA 2000, BA 2000, TU 9900.
At minimum get it checked, contacts cleaned and lubed and re-biased. at least you’ll know if there are hidden issues. you never know when that 40-year-old component will fail and take out the amp section or make it too much to repair.
Always get older vintage pieces at least checked don't be the guy who thinks if it isn't broken don't fix it bull crap. that's how you ruin a good amp.