How well do the older LP-E6 batteries work? I've been stocking up on LP-E6 NH because of concerns about the performance of my older LP-E6 N batteries.
The old LP-E6 batteries work absolutely fine in my R5. I haven't done a frame-count to test the difference between LP-E6 and LP-E6NH, but I can't say I've noticed any difference - I can make either last for a full day's shooting (up to 1000 shots), and some of my old LP-E6 batteries are 2-3 years old and have been recharged hundreds of times. The main difference I've noted is simply that the LP-E6NH batteries recharge noticeably faster.
I recently returned from a 9 day trip photographing butterflies in Kenya, using my R5 and EF 180mm macro throughout. I always fully recharge my batteries the night before. Some days I had an LP-E6 in the camera, other days an LP-E6NH. I always carry a spare, but I don't recall ever having to swap batteries part way through the day on this trip. Daily frame counts varied between 200-1000, with a total of 4500 shots taken over 9 days. Shutter mode was EFCS. I always shoot in short bursts, as I bracket my exposures. Everything on the camera is setup for minimum battery consumption, although it isn't in "ECO" mode.