I have the 6 gallon. Mine only has one drain on the bottom. I'll strain mine every 5-7 cookings through a copper coffee filter. All I use is peanut oil. The batch that's in there now has been in there since Thanksgiving of 2012. Usually when I strain it's about a gallon low. I figure it gets rotated enough to last for a while. Fish, chicken, pork chops, a few turkeys , all fried in that same oil. All taste good.
Probably do need to change it all out and give it a good scrub. Cost $70 to fill it up from zero.