[octobus2021]

I don't consider unlimited battery life (meaning battery will likely last longer than the watch itself), water resistance, and ruggedness to be part of "casio purism". I don't want to charge my watch daily or weekly, like I don't charge my clothes or shoes or umbrella.

[gambiting]

Then......good news, you don't have to do this with this one! If you use it as a watch, and only use the fitness functions sporadically, then it will work forever just off solar power, like any solar powered casio for the last 20 years.