The idea of leaving batteries on a wall wart all the time makes me uncomfortable....too much can go wrong....the timer could fail....thermal runaway on a NiCad......yes it is different than charging over night as with an over night charge you at least see the batteries and charger 15 to 17 hrs......I have heard that you can loose up to 30 percent of a charge over night...30 minutes a day just wouldn't return the battery to a full charge...
Instead why not pick what you're going to fly the night before and stick with your choice or use a quick charger if you change your mind.......
I'd never leave a Lipo unattended....I've seen those burn a couple of times...
But this is just me.......good flyin