These statements of *MY IP hasn't changed in XXX days, months, years" don't mean much.
While it is true a lot of IP's do not change even though there lease expires and renews. However, that IP/MAC address are tied together at the CMTS back at your cable operators OTN/Head end. Understand that if when a CMTS card is swapped due to failure, if the operator changes from a DOCSIS 3.0 to 3.1 CMTS (which is a massive project occuring right now within Comcast, Mediacom, and Cox presently in the US) if the Fiber node you are fed by is rerouted to another laser, etc then your IP can and will change. While to select users this doesn't mean much, however understand that it is quit possible to have any of the above take place, so assure you have the
tools in place to not be effected by this.
Don't blindly rely on your IP not changing - this is why DNS services exist - both free and paid.