Hi Nick -
I'd recommend putting the Tivo on a UPS. Frankly, I'm surprised that consumer DVR's work as well as they do. They are basically computers, with standard hard drives running continuously 24/7/365. They are rarely plugged into functional surge protectors, let alone a UPS. In most cases they are plugged into the same exact outlet that the TV, stereo, and the rest of the AV equipment is sitting in the TV room (which is likely not rated to handle all of those at once, and when one of the larger pieces of equipment is switched on, there is an immediate effect on the other devices on that same outlet).
For best reliability, plug them into
one of these and they will last for years with minimal issues, well past the time you'd want to replace them for ones with better features anyway. That Amazon price is pretty high ($60 or so), and you can likely find one locally that will do an equivalent job in the $40 range. Our UPS's trip at least once per day, and sometimes several times a day. Put that amount of power fluctuation into a hard-drive that's running continuously, and periodic glitches along with an early failure are pretty much guaranteed.