Rechargeable Batteries
Regarding laser batteries, the 8 and 60mW lasers will last some weeks before recharging.
If you use the 100mW a lot particularly on laser therapy, the batteries will not last very long before recharging is needed. Make sure the second battery is charged so it can be immediately swapped for the other cell.
Non-rechargeable Batteries
Non-rechargeables particularly the Lithium cell for cameras will last a long time but may leak if left in too long.
The repair is not covered under guarantee, but if changed say monthly leakage is unlikely.