I get about 3 to 4 years out of a battery on average, which equates to about 35K to 45K miles.  Historically, I've not used battery tenders; I've just ridden it every day, which keeps the charge decent.  Since I've been in actual seasons the last couple of winters, I got a tender to hold it up when I can't ride it (and to help make sure it's as charged as it can be when I can ride it, but it's 30ºF out and it doesn't much like that).

A lot of what does in motorcycle batteries is vibration.  So they can last quite a long time if they are kept tended, but don't get ridden a lot.  Likewise, if the bike is smoother it is likely to be easier on a battery and help it last longer even if it does get some real miles under it.

And of course the quality of the battery itself matters.

PhilB

This set-up has been going strong for a while now.....

My stock 02 battery just died this year. I never had to use a battery tender either. I have been through two batteries since!