How much playtime does one usually require to beat S.T.A.L.K.E.R - Clear Sky?
Depending upon how many times you eat hot NPC frag grenade, you can expect it to take less time than either of the other STALKER titles. It took me about 10 ~ 12 hours to get through all the areas and beat the game.
Also, if you played the original STALKER, you might spend less time because you know some of the original areas that are being re-used.
I should also point out that depending upon how many caches you decide to go after, this can be extended by about 10 hours, but that also depends upon how often you use the guides to quick-travel. Walking will take a while, but quick-travel costs money.
Well, it took me about a a week and a half. But also consider that I had to go to work everyday. S.T.A.L.K.E.R rocks any day what say?