Yes, of course! Best practice is to know about all the obstacles I passed yesterday before they become visible today; to see all the new ones as soon as they become visible, to see all the potential ones before they happen, and so on. Those of us who've been commuting by bike for 35+ years without incident have made this second nature. In order to do this, I use all the tools available to me; including a mirror.
My point was there's plenty of time to look behind you and check before moving over. Even with a mirror in a vehicle it's still a good idea to turn your head and do a shoulder check before moving.