That’s what I do. And LE actually supports wildcards, so that’s no problem. If your local network is firewalled off LE can still issue you a cert so long as you use DNS record validation.
1. Maximum cert lifetimes are falling, once upon a time you'd just pony up the cash and get five years. A year ago it was 36 months, for a few months now it's been 825 days, and there is downward pressure. So you are still going to need to renew this cert, and that means...
2. You can and should automate. Imagine buying a device in 2018 that expects you to manually input an IP address because "Eh, we could do DHCP but this was less effort (for us)". That'd be crazy right? Time to feel the same way about certificate automation.