Maybe, but there's little difference in economy.

The lifespan of a water heater's tank is largely determined by the amount of thermal shocking it endures, and that's directly related to the sizing of the tank. The larger the tank, the smaller the drop in temperature in the tank when hot water goes out and cold water comes in, so the smaller the thermal shock each time hot water is used. So, by using a 60 gallon tank for one bathroom instead of two, you SHOULD expect to get a much longer lifespan of the tank in that heater. I don't know if it would be double, but it would be much longer than using that one tank for both bathrooms.

So, it's a pretty good overall gameplan in my books.