Late game boredom: What does one do with fifteen full resonant energy cells?

I've been playing the same file in d20 for about a week, and with three enormous steam boilers running constantly, a completed hollow hill quarry, a completed nether quarry, and an ender quarry eating up an ENORMOUS area in a mystcraft age, I'm pretty much good on supplies. 12,000 iron last I checked, for example.

Ive been working on building a new base and organizing the tanged mess that was my spawn base, doing some aesthetic building, getting into thaumcraft a bit, all that.

However, I...

Late game boredom: What does one do with fifteen full resonant energy cells?