It's a lot anyway. Although peak power is not great.

Over 5000 years the output would be a few tera Joules of energy. The first prototype used nickel-63 (see https://en.wikipedia.org/wiki/Diamond_battery)

It could be interesting coupled with an ultra-capacitor, if you have something that has sporadic high energy demands, but not always. Think a remote sensor, or pace maker, or such devices that need a short spike of power, but on average the energy requirements are not huge.