I wonder how well Eneloop batteries do against leakage?

The newer white Eneloops ought to retain 50% charge for five years which is not far from the rated shelf life of today's Alkaline primaries. Five years is long enough to consider for lifeboat / emergency / survival applications.

Eneloops might be an (expensive) way to avoid leakage damage to (even more expensive) devices without the hazard of Lithium cells. It might be worth considering in a high-humidity / outdoor environment.

PS. My main worry with Lithium cells is poorly-made counterfeits. There's a profit in using cheap cans or cutting corners on material purity, which matters a lot in Lithium cells.

PPS. Tenergy makes LSD (Low Self Discharge) C, D and 9v secondary cells. These might be applicable in kits that get refurbished annually, at least until Duralock is established.