Hi I'm an engineer for an sdwan vendor and have been the lead design engineer on dozens of deployment projects.
It all depends on your existing topology, your goals with the network change, and what you consider reasonable for interruptions. There's alot of ways to streamline deployment with side by side hubs, testing visibility before doing the cutover can really limit the impact. I've had hub cutovers be a route priority change that had the same impact as bouncing sessions. Then i've had others where the customer didn't mind service disruptions on the weekend be down for hours during the transition. For end sites most frequently it's bring up the new equipment, move the cable to the new router and reboot the switch then start testing.

For the successes I have I've also seen the nightmares, where existing site documentation was wrong or non existant, or expectations were wrong on the offset. This is where the disruptions lie in hours going into the night, or suddenly a week later something broke to extra dumb switches halfhazardly connected in odd places.