Taking my time, I'd guess it takes me maybe 10 mins or so for a total changeover, more or less.
It takes very little time once you get the hang of the Dillon's operating makeup, or if you have the toolheads setup before hand.
I've had Dillon's since the early 80's and now I have three.
The choice back then was based on reviews, word of mouth and as much research as could be had at that time. It was sound, and I've never had any regrets with their equipment. Their warranty, although rarely used, is second to none, and Dillon's staff is phenomenal.
I started with a RL450, and later upgraded that to a 550B. In between that time, I received a Square Deal B and another 550B. I can switch components between the two 550's, and keep the Square Deal for loading my most used pistol rounds.
I also have a single stage press, as well as a turret, both Lyman's. I've found that I use the single stage press more for loading my rifle rounds "singly", and the turret gets used for those few special pistol rounds that I need now & then.
Good choice.......
Take care,
Bob