Hamstrings shouldn't take too long to stretch out by themselves.
But not to beat the drum yet again... things rarely become tight in isolation. So I would concentrate on more movement and sport specific stretching. So you're pushing movement patterns rather than muscles.
So stuff like wall stretches and just sitting in the bottom position of the squat with an unloaded barbell for 1 minute at a time. That way you don't need to know exactly what's tight, everything relevant gets stretched.
Certainly some muscle specific stretches alongside that can help. But the movement specific stretches will ultimately have more impact quicker.
Last edited by Fazc; 02-19-2013 at 06:01 PM.