Eh, I gotta disagree on the cast iron thing. That warped grate on mine was cast and it lasted three summers before it got bad, while the cheap steel one's been fine and it cost way less to replace. Spending more on heavy cast just means more money when it warps anyway.

Who knew a twelve dollar tank from some stranger's driveway would outshoot half the gear on those forum threads? I just fill a plastic tub with hot tap water and drop my bottles in, then check with a cheap digital thermometer every few minutes and add a splash more hot water when it drops. My kitchen sink holds temp way better than I expected once the bottles are sitting in there. Temp control really is 90 percent of the battle.

Are you sure it was the batteries, though? I have run cheap lasers until they died and they just shut off rather than quietly giving you bad numbers. Low voltage usually makes them blink or go out completely, not slowly drift like that. Sounds to me like the unit itself took a knock or the pendulum got sticky, which a pricier self-leveling one might handle better but honestly still isn't guaranteed. I would test that same laser with fresh batteries on a known straight line before trusting it again, because chalk lines are great but they will not save you from a tool that is lying on a warm day.