Here is a new Home Depot review that was done on the larger unit. To answer his concerns, the unit will last decades and squirrels show no interest in it. Also a roofer will charge between 150 and 300 dollars per unit to come, remove shingles (a dangerous proposition that can cost a lot more to fix) and put on another lead flashing only to have it chewed up again. Based on that a 30 dollar Critter Quitter is a bargain. Here is the review

I don’t know how it will hold up to the squirrels but it was easy to install after you cut it for the pitch of the roof. A bit pricey but easier than replacing the lead boot.
Pros: Easy to Install, Easy to Use, High Quality