On long smokes I use one of the spare aluminum drip tray pans that came with my smoker for grease off in the corner so my meat doesn't dry out. I always change my foil out before every cook. I have never noticed that the drippings from my food give me any sort of "off taste". I have heard of guys being lazy and not changing their foil after a smoke and then having an off taste when they smoke something else because those drippings from the previous smoke start to heat up and ie if it was beef and now your doing pork you'd prob have an off taste. Just my 2 cents.