I would be concerned, if leaving the a/c unit in for travel, that you would get an 'oil can' flexing that could cause failure of the f/g.
Between the PO's unit in the dinette window and my upgraded replacement of that the AC a year ago. the AC has been permanently in place in the dinette window for 28 years with no ill effects to structure or fiberglass.
I was concerned about that however, so when I redid the mount I sandwiched all the edges of the fiberglass with 1 1/2 aluminum strips inside and outside to reinforce the mount to the fiberglass surfaces.(You can see the outside strips in my earlier photos) You can lift the trailer off the ground now by the AC, although I wouldn't recommend that as a regular jack point.
On these temporary window mounts, I would certainly not recommend leaving them in for travel.