Lg Warranty will probably still cover it. There are tons of users with the G4 or nexus 5x with the bootloop issue that have shared their concerns on reddit.
As for another phone, I would say avoid anything from LG, even though they are one of the easiest devices to root.
As of right now my v20...
I had to "replace" the fan in my coolermaster 1200w with another fan. It was 135mm and I just used a 120mm fan and connected to a fan controller. It worked great for years.
I have used a an lg g2, lg g4, nexus 5x, and currently on a v20. I have never ran into any bootloop issues at all. *knock on wood*
I still have the g2 , n5x as well for back up devices.
honestly the 5870 still has life in it. if you don't mind running cf for a bit i would look into that. but upgrading it right now would be a little late. so waiting might give you the upgrade bug but at the same time when the new line up of card do come out it would be a more notable performance...
for me, its pretty much the same story. i end up paying my games in windows mode in order to multitask. it was definitely fun when i had it as well and as a teaching fanatic it was most definitely amazing. i was also only using 6870's in cf
i wouldnt have done that only cuz the fact of the facet water has other minerals that could lead to other reactions with your blocks and rad.
cleaning with distilled and vinegar soak is better fyi =]
well i can tell you this based on personal experiences. i jumped on the phenom x4 9600 i thought it was good enough for me. then i started tampering and figure out to over clock and it didn't turn out so grate. Further more those chips had the infamous TLB bugs and pretty much lock up and fail...