It's all well and good basing the DND around the users bed time and wake time, but you allow different alarms for weekends and weekdays. Would it not be better to say the if the alarm is set Do Not Disturb stays on until the alarm, otherwise there's point in the alarm...
(In case you're wondering, I have and I use a Forerunner 630, so I'm answering only as a fellow user who you'd imagine has the same concerns as you but don't.)
