This is another question regarding "the popular $20 headlight" (someone added a post right after my question in that thread without addressing my question so I'm starting a new thread):

To prolong the battery lifespan, what's the best to use this light, if I have two battery packs 1 & 2 for the light?

a) charge 1 fully, use it half way, set it aside and use battery pack 2 from full charge until half way, then set 2 aside, use 1 (after fully charging it).... In other words, always use them from full charge to about half way, never use it all the way to totally discharged.

b) charge 1 fully and use it all the way to totally losing the charge, then use 2 (fully charged) until half full--meanwhile, charge 1 to about half full and keep it waiting---because I read that lithium battery should be kept partially charge when not in use. Then charge 1 fully before using it. In other words, always use each battery pack from full to no charge.

(Real experience should make more sense than theory )

(btw for that damn tight connector, I have to use pliers to disconnect it after each ride )