Only if you hide it in a highly public spot. Any mechanical clock, with ticking loud enough to be heard from inside an ammo can, is gonna be a battery hog. If you hide this way out in the woods, where the numbers oriented cachers rarely roam, the batteries will die betwixt finds. Put it somewhere that the P&G crowd will appreciate, like under the steps of a courthouse, next to an active rail road track or under a highway overpass and you'll be fine.
I've been thinking about making a HUGE geocache and one of the local elementary schools gave me permission to hide one one their property. I'm think about taking an old van, the kind that is big enough to use as a camper, and parking it outside the school and hanging a sign that says "Free Candy". I really think the kids will appreciate it and it should get lot of favorite points.
Dude! That's an awesome idea!
You should paint the windows over so muggles can't see the cache inside...
And put a mattress inside so cachers can rest after they find it...
And then ask walking by kids to help you find your lost puppy!