Isn't that risky? The subscriber number will sooner or later be recycled for another device (in the case of burner phones) or customer (in the case of voip). They could in turn disrupt your Signal use.
Definitely a hassle, but for anyone for whom a phone number is insufficiently anonymous I would imagine they're used to it.
I admittedly don't know as much about the options for VOIP but I've got to to believe there's a way to get a phone number on the internet where you can receive SMS and keep it active indefinitely.