Seems strange that your storage is warm and yet no power!! where you are the atmosphere is dry(I have a relative in Finland) as opposed us Brits who have to put up with the damp,most certainly change the oil you don't want to be leaving it for that length of time with used oil in,I'd drain as much fuel as possible modern day fuel goes off in around 6 weeks put fresh in when you use the bike,and yes taking the battery off and charging else where is no problem.