Any battery left unattended will deplete over time lessening the overall life regardless of temperature. The best thing a person can do to extend the life of a battery is utilize a battery tender to prevent this from happening. They don't cost a lot of money and costs are recovered in time due to replacing less batteries.

MikeSomething, that is about the worst thing you can do to a bike. You should never start it up and then just leave it ticking over. That does not help the charging system, they are not efficient and actually charging until over 3-4k revs. Then the just leaving it to tick over, the oil does not fully circulate around the engine when just ticking over, you need to rev it and ride it for that to happen. So you are not only helping deplete your battery but also accelerating engine wear by doing that.

I usually start my bike up every 5-10days and just let it run for about 10mins. It helps the charging system and I'm sure the engine heat doest hurt either. If you're leaving the bike outside in the weather, just unhook the battery and bring it inside just for peace of mind.