The audit and management features of an electronic access control system already make mechanical keys inexcusable on any door that >1 person needs to open. Hopefully revelations like this will push more organizations to upgrade.
Either way, the owner almost always has a key that can mechanically override the electronics and open the door, but this is kept in a safe, rarely used, and will set off the "door forced" alarm.
Without getting into the discussion of the security factor of biometrics, the working mechanism of the lock itself is such that when it detects a success, a small servo engages some sort of a gear which enables you to complete the mechanical circuit (so to say) when you push the door lever down and move the physical lock with human effort.
This means that the battery is never constantly used, only when the actual sensor is active. Even if it were dead, there exists a manual key override. Also, (I've tested this personally), the factor of safety is quite good in that, the lock starts beeping "LOW BAT" a good 3-4 weeks before the battery is completely drained. Also, (Another one) it doesn't leak information about low battery until there's a successful entry, so an evil attacker can sit near your house activating the sensor all day and he won't know his progress in draining the locks' battery.
Edit: it seems electronic locks that come on top of the existing lock tend to have the battery pack inside, while electronic only locks can have it outside. BTW the batteries are supposed to last two years in the product description (that's in line with what I had too) I was mentionning these kind of locks:
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