what is cage size? what type cage is it? glass/wood/platic.
what is all around temps? hot spot/ambiant/cool end.
Does your snake have a hide? both on hot side and cool side?
Have you checked for mites? Do you mist the cage often or do anythign to raise the humidity?

in my experiance when a snake is in to large of a cage/ or temps on hot spot are to high/ doesnt feel secure/ or has mites it will soak quite a bit instead of just awhile here and there.