Allowing for the caveats expressed above eg by eb, threads in 5.8 seem fine to me.
I wrote a threaded daemon for an ISP for tracking user's packet usage via netflow/RADIUS which runs 24/7 and it's been running fine for 1 or 2 yrs iirc (I've moved on a while ago).
Just need to be careful and I'd also recommend having a stable num of thrs and re-using them, rather than creating/destroying thrs to be safe.