I don't know about the hardening features of Foma films, but I've used both hardening and non-hardening fixers with them, with no obvious problems with the non-hardening fixers.
As to washing times, IIRC 30 minutes is a fairly typical recommendation if you don't use hypo clear. I've always used hypo clear and either a 5-minute wash (with hardening fixers) or the Ilford method (with non-hardening fixers). Like Roger, I repeat a step or two just to be on the safe side when I use the Ilford method. My oldest Foma films are only about a year old, though, so if I've been underfixing or underwashing I might not have noticed problems yet.