I think everyone is going to be a bit different. The only time I have difficulty playing the same song across on another accordion is only when it is new to me. The exception to that for me was the first time I put on the Beltuna Leader V. I was "at home" near the moment I put it on.
The first time I played the Imperator, it was almost challenging, I had to work hard mentally to get it to play for me, the same for the Gola, it was almost foreign to me... but that lasted about 3-4 hours since it was brand new to me after all. After that I can transition back and forth without near any issues... perhaps a minute or two to regain the "feel" of that accordion, then its all good from there.
I can transition easily from my Elkavox to my small Hohner FB36 to the Beltuna and to the Morino without thought. I just run scale or chording or two and I am good to go. The Gola is the accordion that I have played the least, but already started to get comfy before I sent it off for it's checkup. When I get it back (hopefully before Christmas), I should not need more than a couple minutes before feeling fully at home again.
With 14 accordions in my collection, one would think that it takes a lot of time to get comfy with them all, but no, not really. In general when its a new to me accordion, 3-4 hours before its like wearing my own skin (I have to REALLY like the accordion to form my bond with it!), and after that, only a couple minutes if I have not played it a month or more. If its like a few days or a week, no acclimation time needed.