Over the past 11 years (i'm getting old!) I had about 50 reps with maybe 30+ of them based on a7750.
None if them died on me. Some had problem (power reserve, chrono that stop after 40-50 second, etc) but I think only one developed a problem. The other had their problem at arrival and I was too lazy to send it back. None stoped working.
Out of 15 reps I have right now, half of them are a7750, and all going strong.
I guess I'm just lucky.