Both times I've had it done, it was every 15 minutes during the day and every 30 minutes at night. Approximately, anyway. I tend to go to bed later than the settings allowed, so the last couple hours I'm awake I get tested less.

And yes, more comfortable wearables would be grand. Blood pressure cuffs hurt: Last time I had the 24 hour monitoring, I had bruising and blisters from the cuff.