there are two states that lipos get harmed at if not being used ,one is fully charged ,and the other is at a very low voltage
these two extremes cause the battery to gradually lose its ability to hold a full charge ,and indeed take on a charge
two other external influences that are harmful to lipos and restrict their performance are heat and cold so do not store them in a very hot place, cold limits their output performance ,but some people believe that low temp storage slows down the loss of charge, and recommend keeping them in a fridge when not in use
as far as the UK is concerned we don't often get the extremes of temp that would need such measures
for me i like to land at around 40% which gives me a flight time of between 18 to 20 mins ,they are then at a safe storage amount till the next time i fly
whether it is in a couple of days or a few weeks if after 4 weeks i had not used them then i would check them to see how much charge was left
don't become obsessed with worrying about your batteries as DJI has put in place some built in safeguards to protect them happy flying