We've been told to charge all of our instrument and data collector batteries every day, including weekends, whether we've used them or not. Equipment used includes the Topcon FC-5000 and Topcon ES-105. The field crews disagree because we're concerned about ruining the batteries. Opinions please.
The batteries we use today, the manuals tell us to keep them plugged in. After so many charges, you do a recycle on the batteries with the charger.
We hope the manufacturers make the chargers smart enough to properly care for the batteries. That process depends on the choice of battery chemistry, so we shouldn't mix types of battery without a lot of research into compatibility.
I know that my old Trimble Office Support Module is made for Sealed Lead Acid batteries and it charges them with current limiting, up to some voltage threshold, and then drops to a lower maintenance voltage that is typically recommended for float on that chemistry.
If the charger has some sort of indicator, typically a colored light, that tells you when the battery is fully charged it will also have circuitry that cuts the charging to a trickle when the battery is fully charged. Leaving a charged battery on such a charger won't hurt battery life.
Even so, buying new batteries a little more often is much cheaper than being caught out with dead batteries, even once.