I am having an old J2 which we had bought for my younger brother 5 years ago. It's still works fine. My earlier J7 prime also in a working condition.my friends J series Samsung phone bought in 2018 still running properly. another friend's S8 phone still runs properly though battery life is only for some hours - he enabled dark screen mode it helped save to some extent battery. may be i guess its related to software updates it might cause problems by some extent due to unoptimized properly for battery optimization & apps, cache. my friends enable battery saver mode in j series phone.
I think if we maintain it properly then it won't have much problem for few years for sure. or maybe earlier they used to manufacture of standard quality nowadays they don't do it with that perfection as earlier when they were new.
I never even heard of such motherboard issue before.
It would have been okay if 1 amongst 1000 was facing the issue. But if almost everyone after 1year facing these issues, it seriously questions the quality.
Another thing to note here was they had launched this phone exclusively for India maybe with compromised quality.