I am planning on going all grain after several extract and specialty grain brews. I am thinking of using a 10 gallon Rubbermaid round cooler for an MLT and a second one for HLT and found a couple of these coolers at Home Depot ($38 a piece!). However, I've read on a number of posts that these coolers warp either initially or over time. My questions are, how bad does it warp, does it effect the amount of volume in the MLT or HLT, how long can they be used before they need to be retired... I want to get a set up that will last a long time so I don't have to upgrade any time soon. Any advice out there?