I hadn't seen this, thanks for posting!
Hmmm may be worth considering...
The "fine print" on the website regarding cancelation reads:
The 25,000 United Mileage Plus Award Miles are awarded 40 days post purchase as long as Customer does not cancel or return their kit order within the 30 day money back guarantee period. Mileage will not be awarded for cancelled or returned orders. The 100 monthly United Mileage Plus Award Miles are awarded for each month that Customer is an active paying subscriber of LifeShield professional monitoring services. Mileage Plus awards may take 4-6 weeks after award date to reflect in your United Mileage account.
I'd read the bolded text as saying that after 41 days one could cancel and be good to go (assuming the miles post by then). The next sentence is more broad but in context with the prior text hopefully wouldn't mean forfeiting the miles if you cancel after the 40 days.
However, given the last sentence...may have to wait longer as I'd sure want to actually see the posting in my MP account before canceling.