I have >15,000 miles on a standard Nexus 8. It has been submerged several times (riding in flood conditions.) It has been running unauthorized synthetic lubricant for all 15,000+ miles.

It was loud when I bought the bike (used) and it is still loud today, but it hasn't really changed for the worse. This summer, I started having trouble keeping the rear wheel from sliding forward in the drop-out. I'll just start carrying a longer wrench I guess.