Does it drain the battery when it's not being used? i.e. Would the battery last longer if the keypad is only used once or twice a week?

The batteries in the SmartCode 913 should last 6 to 12 months, depending on usage. If the batteries are draining quicker, here are some steps that will help you: ensure that your door is properly aligned and that the jamb hole is 1 inch deep for the latch to fully extend and prevent jamming, which can cause batteries to drain. Also, please ensure that your batteries are alkaline, avoiding lithium and rechargeable batteries.