Throughout the summer I'd fly many of the same planes day after day, week after week. If I didn't manage to use all the batteries for a day I knew I'd use them the next day or within a few days so I did not discharge them into storage mode. Over the last few years I've never noticed any harm to a battery in keeping it charged for a few days. Today I went through all my batteries and found 15 with a 70% or more charge so they're all going into storage mode now... ready for next year.
same with mine, all around 30% even the ones i didnt use on friday.