Running 10 S5 on f2pool now and no reboot needed so far. The others on nicehash keep crashing, seems really pool related.
Nicehash was working great for all S3 for months, never had an issue. Only the S5 have problems.
I'm running 6 S5s on kano main and extranonce with p=0125 on westhash and I've only had one issue in the last month, all 6 s5s were about 100g/h less than they usually were after a series of rapid switches over a day, I rebooted them and moved my p= amount up a bit to stop switching.
I'm running smit's firmware with cgminer 4.9.0