Can I leave my radio on in the charger during the day?  How about at night?

Generally this is not a good practice.  The battery is designed to be charged and then depleted through use.  If you leave it on in the charger you are actually charging and discharging the battery simultaneously.  If you leave it on overnight, the charger will charge the battery and shut off.  Your radio, still on, will be draining the battery so that in the morning, you may only have 50% of the life left.