After building 3 versions, my opinion is that to build a longer one and retain the rigidity I got would require more than 1 linear actuator. If true, that makes the control program much harder and getting everything in synch might be tricky.
I read some info on a table that was 8 ft long and the author said it was very wobbly. My tracks are 46” long and that seems pretty good for a medium size layout.