What kind of batteries are we talking about here? That will effect what you need to do.
Lithium Ion, the most popular batteries in digital cameras and cellphones will lose charge if not in use. Even if taken out of the device. The reason is they have circuitry in them that prevents them from overheating and exploding, and that runs non-stop. Remember the Samsung Galaxy Note 7? That's what happens when you don't manage a Lithium Ion battery properly. Lithium Ion batteries also don't like to be run until their fully dead. Sometimes, if they're completely drained, they may not come back. Hence why most Lithium Ions will shut off before they are fully drained. So it's best to charge these before they completely die, which means you might want to charge these on a schedule if not in use.
NiCd batteries don't mind being fully drained. In fact, they love it. They have a chemical memory and fully draining them helps to reset their memory. So if you only drain a NiCd battery half way each time before recharging them, they'll eventually believe that half way drained is fully drained. So it's best to let these completely die before recharging them. They don't, however, lose much charge if they're just sitting around, not being used. So I wouldn't charge these unless you know you're going to be using them soon.
I'm not sure about NiMH batteries. I rarely ever use them.
Most rechargeable batteries die due to heat. So leaving them on the charger is a bad idea unless the charger automatically shuts them down. It's also a bad idea to leave them in your hot car. That's why trickle chargers are usually a good idea. They don't overheat the battery too badly while charging. The bad part of a trickle charger is if you leave the battery attached to it long term and don't remove it, then you're generating unnecessary heat and slowly destroying your battery for no good reason.
So probably the best course of action is to just charge your batteries the day before you need them. If that's not convenient, then I'd buy several batteries and figure out a regimen that suits yours and the batteries needs. With several batteries on hand, it's less important that your batteries be fully charged before each shoot.