My chevelle sat for eleven years and all seemed fine with the gas tank for the small use I gave the car the first year. After going through everything on the car and taking a few rides of more than a couple of miles I started to have a problem. Apparently the "crystallized, smelly, brown junk" was slowly becoming dislodged and intermittenly causing a fuel pressure problem. I was carrying spare filters and changing them frequently( I even added a filter before the pump). Eventually changed the pump and then the tank and lines after a year of being unable to get the tank clean. (The local shop said the tank was too far gone to clean.)