After recent discussion about FTL travel, I started thinking about G'father's 'pocket universe/s'. (I think if there's one there could easily be more, who knows?)

Anyway, the one we know of for sure in the TU has been in existence 100's of thousands of years, right?

So the stars/suns contained in it have  pumped out an unbelievably enormous amount of energy into a basically 'closed system'. (no 'expanding universe' here, AFAIK)

So what happened to all that energy?

Both 'conventional' & TU 'handwavium' speculation welcomed!

TIA,