Others' experience may differ but I've never used a battery tender or the like on my Beemers.
My first battery (original one in '90 K75RT) lasted 7 years and the only reason I replaced it was because it was 7 years old. I wish I'd a kept it cuz the next BMW battery lasted about 2 years and left me stranded.
By, "leaky electrons" I was referring to things like keeping the ground lug under the tank tight and clean. A lot of electrical issues can be traced to bad grounds. There's the big connector on the FI unit that will sometimes lose connection. Old Hall-effect sensors that eventually go bad. And, things like that.
Electrical issues or additions of electrical gizmos are a common theme on BMW Motorcycle sites.
I was thinking about it the other day, and about the only "special" tool I have for the K's is the oil filter wrench. Who knew!

Tom