To a first approximation modern li-ion batteries don't really care if they drain 100->50 once or 100->90 five times: the wear on the battery is more or less equ

To a first approximation modern li-ion batteries don't really care if they drain 100->50 once or 100->90 five times: the wear on the battery is more or less equal. Exposing your batteries to extreme temperatures (below freezing, above 40C) or allowing them to self discharge below the safe low voltage limit has a far greater impact on overall longevity.