spasms from deadlifts and hyperextensions are gone in 10-20 minutes, thank god. My deadlifts suck though, my ex-gf deadlifts 20lb more than I do, and with better form. Squats I'll have tightness almost 2 days after, but no pain.
After you work out for several weeks, I think what is going on in the muscles stays the same but eventually you kind of get used to the feeling of soreness. Either that or you've kind of hit a plateu where you're not growing as much anymore.