According to my prvious bike's manual (Kawsaki Versys)... the colder the temp the less the battery discharges... Not below freezing however... around +8C to +10C seems to hold it's charge the longest... As the temp increases, you will need to charge it more often... I can confirm this... My garage hovers around +10C all winter long... My '09 V-strom started up perfectly after 2 winters (battery voltage after 3 months was 12.6V) each being after 3 month's of storage with the battery left in the bike and no charger attached...Considering the crude charging system on Stroms then yes its fine
If you put the bike up for the winter it really needs a trickle charge at least 2 times to be healthy. If the battery is allowed to go cold then it is damaged and life is reduced.
during midwest winters i keep mine on a tender. original was 6 years old and still showed good. if you have several toys, replacing every three years is an expensive waste of money to me. but, to each their own !Needed or not, I change the batteries in my bikes at 3 years... Nothing like have one take a crap and it only happens in the worst places - of course!