How many do you use simultaneously?
Usually just one, so it is not too hard to accidentally end up with zero on-hand.
How many do you own "simultaneously"? When I decided my 305 hadn't actually died, I owned two working watches. The 310 is quite an improvement though. The neglected 305 has an uncertain future, like most older technology items.
I have often needed to get new models when people run into data issues or other quirks that I can't replicate with what I already have.
So I am up to around 15 working ones, including some non-Garmins.
> Usually just one
I'm somewhat disappointed by this answer.
With the surfeit, I considered pointing out possibility of an AP "yard sale", profits to the juniors.
There must be some kind of way outta here. Maybe you could build a tower an place them all along it?