I had a OnePlus 6T and a OnePlus 8T.
OnePlus 6T: had it for 1.5 years and sold it because it had some weird bugs (can't remember exactly which).
OnePlus 8T: had it for almost 2 years. Updated to Android 12, was shit after few weeks. Factory reset to 11, used that a long time. Updated to 12 for a a few days and then to Android 13. Was alright but again a few bugs. Factory reset it again a few (staying on Android 13). Later Factory reset it to Android 11.
I have factory reset it 5 times in 1 the last year i had the OnePlus 8T.
And despite the many factory resets, every few days had a bug where it became so slow it wasn't useable anymore and had to reboot.
Short story: OnePlus had a lot of potential and I bought a OnePlus 6T for the price and the good software support they had in 2018. I feel a little betrayed because they became so worse over the few years I had my OnePlus phones.
I now have a Samsung S23 Ultra which has good software support and yes it has some bloat. But i don't have stupid bugs and the phone stays fast.