I've had a few flats with tpu tubes, some of which were likely caused by installation error (accidentally twisting them).

I've broken a few of the plastic valves as well (Spingo brand), but I think that was because my pump had was failing and not sealing, and I thought the issue was the valve, not the pump. So user error there, too.

I bought some Ride Now tubes more recently. Of those, 3 of the 4 I bought have been fine. The fourth one isn't holding air, but I haven't had the time to figure out why. Just swapped to another tube to get the bike on the road. I like that the Ridenow tubes include patches.

Short version, my experience is that once they're in and working, they tend to be good for a long time. Gotta be more careful installing them. Overall, I do like them.