Well, my first big spinning project (before I had my own sheep) was moorit shetland tops, and I knitted a jumper from it (in the summer of 2006) - I have worn it most days since then (not for farm work i have to add), it is fairly thick and I have NEVER washed it yet!!! Now starting to get a worn out (and has been repaired several times altready... It is really warm, I do not own a winter coat (or any coat other than water proofs) anymore, so real wool jumpers are brilliant!!!
Anyway re lumpy yarn - as the others say, keep it for special effects once your spinning is quite even and often very thin... although I find some fleeces are just for spinning thicker yarn and others not.... not sure how to explain it. You can always use several strands of wool if quite thin, should make a warmer jumper in the end.