> It's about as renewable as solar, which is to say, we will eventually run out - but at that point the heat death of the universe is a more pressing concern.

Nitpicking:

The sun is expected to stop fusing helium in about 8x10^9 years [1]. The heat death will occur in around 1.7x10^106 years [2]. (if at all, there are some uncertainties around that)

Which means that while they are both far, the heat death as predicted is much much further than the other. In short, the heat death of the universe won't be a pressing concern at all when we run out of solar.

1: https://en.wikipedia.org/wiki/Black_dwarf#Future_of_the_Sun 2: https://en.wikipedia.org/wiki/Graphical_timeline_from_Big_Ba...