Well, Wikipedia claims
The Earth has an internal heat content of 1031 joules (3×1015 TWh), About 20% of this is residual heat from planetary accretion; the remainder is attributed to past and current radioactive decay of naturally occurring isotopes.
In that sense, it’s the only renewable energy source we have that’s not indirectly powered by the sun. It’s most similar to (proper) nuclear power, but the latter isn’t “renewable” because it requires digging up fuel from the crust.
It’s just the time the manufacturer is willing (or forced) to be held liable for certain defects to be caused by manufacturing errors instead of expected wear and material degradation.
Unless something is mission- or safety-critical, replacing it before it breaks is wasteful.