Fulk said:
When using 18650 batteries, is it best simply to use/recharge or to run the battery down completly (occasionally?) and recharge from scratch?
Lithium Ion batteries cannot be discharged completely. There is a minimum voltage limit, usually controlled by electronics, of about 2.5 volts, individual manufactured cells may vary. Discharging below that level will destroy the cells and absolute discharge may cause internal short circuits that can cause the cell to explode, especially upon a charging attempt. This is why 'Protected cells' are recommended. But dont worry too much, dedicated chargers and the cell protection electronics have built in safeguards.
They do not suffer from 'memory effect', this is mainly a phenomena of Ni MH and should be top up charged before any mission critical use.
As a point of interest, phones and devices usually come with apparently 'flat' batteries. No so. They are electronically disconnected and the circuits 'activate' upon charging.
For any device, read the manual.
Final lesson from a recent lamp sale
Customer. How do you..........................
Me. Its in the manual
Customer. Oh, I threw that away