I do get nervous about trapping moisture under the boot—had a patch of moldy decking once because water got in and couldn’t dry out.
That’s been my biggest concern too, especially since I’m in a colder climate where things just don’t dry out fast. I tried the “thicker bead” method as well, but it just seemed to crack worse after winter. I ended up switching to a flexible polyurethane sealant instead of silicone, and it’s held up a bit better through the freeze-thaw cycles. Metal boots are tempting, but the price is hard to justify unless you’re already replacing a bunch at once. For now, I just check them every spring and touch up as needed... seems like the most cost-effective route unless you’re dealing with constant leaks.
I’ve been wondering the same thing about how much hassle is actually worth it. My house is only a few years old, but I already had to replace two vent boots because the original ones got brittle and started leaking right after our first real winter. I used silicone at first, thinking it’d be more flexible, but yeah—cracked right along the seam after a couple freeze-thaw cycles. Polyurethane seems to flex better so far, but I’m not sure how long it’ll really last. Has anyone actually had metal boots last more than a decade? I keep hearing mixed reviews... At this point, I just keep an eye out for any signs of water in the attic and hope for the best.
I hear you on the freeze-thaw issues—those can wreck even decent materials. I’ve seen metal boots go past 10 years, but it really depends on how they’re flashed and sealed, plus how rough your winters are. Some folks swear by them, others say they still get leaks around the seams after a while. Have you tried the reinforced rubber collars? They’re not bulletproof, but I’ve noticed they hold up better than the cheap stock ones, at least in Midwest winters. Keeping an eye out for attic leaks is smart... sometimes that’s the only warning you get before things go sideways.