I'm assuming you're waiting until the end of the 7 day battery life to recharge it (e.g. you recharge every Sunday) and I'm assuming the probability of a theft is uniformly random throughout the week. Thus, on average, you'd expect stolen devices to only have half the battery left because there's equally many stolen on the first day (7 days of battery left) as on the last day (0 days), equally many stolen on the second day (6 days left) vs penultimate day (1 day left) etc etc. At scale, that would average out to stolen property having attached devices having half the advertised battery life.

You can argue that you'd be more dilligent about recharging but I'd counter that at scale you'd be the outlier. On average I'd actually expect an average battery life when stolen closer to 0 because people wouldn't be diligently recharging them & reattaching them (i.e. either the battery life would be 0 or the device wouldn't be attached to the desired property).

I don't think people would only charge when the battery runs out. More likely people would charge weekly, say on a weekend night or during their weekly WFH day or something like that.

A 14-day battery life would then mean an average of 10.5 days of protection, which isn't too bad.

> You can argue that you'd be more dilligent about recharging but I'd counter that at scale you'd be the outlier.

I don't know about this. For bicycle users, charging their rechargeable headlights and taillights regularly (typically once weekly) is very much a habit already. This is just another thing to charge at the same time, which is a time they aren't riding their bicycle.