Keyfob battery lasts longer with use?

Every few years the battery gets low on the keyfob I use daily, so I simultaneously replace it's battery and the battery of the keyfob that never leaves my sock drawer. Here's the weird thing:

The battery on the keyfob in the drawer is always stone dead by the time the keybob I use gets low. Why would that be? Any ideas, please?

 

Perhaps, but it's virtually brand new/never been used.

Having just changed the battery last week, I just decided to switch them. Now the virtually new one is in my pocket, and the one with many years of service is with my socks. I'll check back with the results of this experiment; my guess is that switching them won't change anything, and the one in my pocket will still last longer somehow.

 

Maybe something is wrong with the "brand new" one (perhaps a button switch is partially engaged somehow).

If not...if whichever is in the sock drawer dies first, I like the suggestion to remove it's battery. Glad that I guess lithium batteries don't generate that encrustation regular batteries do in my old remotes.

 

(Fascinating; I didn't know communication between the fob and the Prius was two-way.)

Six inches from the sock drawer is a 40" LCD HDTV. Two feet from the sock drawer is a large pair of stereo speakers (when I put them too close to a tube TV, their magnets distort the nearest areas of the picture). The car is far out of range of the sock drawer.

Maybe I should scrap the "switch fobs" experiment and go with the "move unused fob" protocol!

 

I switched FOBs, and now I think Patrick may be correct! (Since the good FOB stayed good in the drawer, and the problematic FOB didn't work as long as a good one would on a new battery.)

Not that any of the 3 buttons appear to be stuck down... (All 3 buttons seem to click/go down identically when depressed on both FOBs.) however...

The lock button on the problematic FOB only lights the red LED every 2nd or 3rd press. All other buttons on both FOBs light the LED every time they're pressed.

What's the best solution, repair/replace? It doesn't look easy to service so I may have too many thumbs for to try it myself. I figure my dealership (Berkeley, CA) will have sufficient experience with this.

 

Thanks you for the well-stated reality check. On my budget, I'll just replace the batteries, particularly since for now it's "just" the backup.

I'll keep it empty in a drawer with a new battery (I just got 5 on Amazon for $2.95). Which mostly I expect to use when the good FOB or a motherboard needs one. Should the backup FOB need to be used, I found that a new battery is perfect for a while (I forget, maybe a few months), and works enough to use with the against-the-skull-trick for longer (I forget, maybe 6 months).