Hi
I have a 540GT with the optional Single beds with pull-out slatted frame and free-standing table. We use the pull-out beds all the time as they are so much more comfortable.
The only downside is the effort required to set them up / put them away each time we move on.

Does anyone know of a good reason why the pull-out frames cannot be left out/extended whilst touring?

We use them as 2 singles. They are left in that setup with the bases pulled out and the split back cushions in place all the time. We have enough of a gap for legroom. The end cupboard door is removed and in the loft as it it's a bit useless if the beds are in the way all the time!
The pic is from our '17 Triton but we do the same in the '04 Troll.
You do need to make sure the legs are in place - they do get moved a bit - I nip my nuts up to make sure they're nice and tight.IMG_0041.JPG - Bild entfernt (keine Rechte)

Yes I the 540GT and have done the up grade I have gas struts to lift and hold the beds up. And heavy duty rollers on either side of the bed frame to slide the beds out. If you search on this site you will find the diagram on how to do the fix.
Slightly fiddley well worth it Morphy

Thanks all