I was using some really cheap lights USB rechargeables with 4 leds each which it turns out run for 15 hours.
£12 in Nov 2021: https://www.amazon.co.uk/gp/product/B0882YB97G



I recharged them about every 4 outings (approx 10 hours) - no battery indicator.

All my TV remotes / shaver / etc run on rechargable batteries so I've got no problem swapping batteries when required.
I just need some warning.