The non-washable hoses do begin to rust and particules will actually be sucked down the throat when it rusts. You will know when the smoke is to harsh, as soon as you take a draw you will cough like never before, if that happens take off some heat and purge the line until your base has no more smoke in it and then either mix your shisha around or just try another draw. The taste should be a lot better. Pase yourself with the smoking, I haven't ever heard of there being to much, except in one study I read that the carcenogenics are 10x higher with 6-8 sessions all lasting 2-3 hours each session, moderation is good. About your hookah and washing, I have always washed the whole thing inside and out without any problems. Once you use your hookah, the shisha smell will always be there, hopefully the stuff your smoking has a strong smell and can over power the last stuff your hookah was used for. Try blowing through your hose after each session and cleaning your hookah when your all done, this will help clear out the smell.