On DOCSIS and PON networks my experience has been that dynamic IPs are generally stable as long as your DHCP lease is active, so my IP generally wouldn't change unless I changed equipment or there was an extended outage that kept me offline during the entire time it would normally have renewed.

On DSL networks it's been the opposite, if the PPPoE session was lost I was definitely going to get a new IP address, and on some providers the session would be reset every 1-7 days so the IP would change at exactly the same time of day which almost always ended up being in the middle of a work day corresponding with whenever the equipment was last rebooted due to some other problem. I got in the habit of setting up my equipment to restart on its own terms in the middle of the night on those providers, but this came with its own downsides when something would go wrong and it'd fail to negotiate.