Interesting. I guess we are odd man out on this one...we put ours down when underway.
Maybe because when we bought the trailer the table was loose from the wall & wobbly. During our restoration we found out why...the two ribs under the window that supported the table were broken completely in half and the skin was all that was supporting the table. Check out the picture at 2:09-2:11 below:
There were also countless holes drilled in the area where the PO had attempted to reattach the table. Enough holes, that we decided to replace the inside skin. After we replaced the broken ribs, we reinforced that area under the new skin with an extra sheet of aluminum, then re-installed the table - but always travel with it down.
We have no way of knowing if the previous owners "traveled-in-up position" or someone sat on the table & compromised the ribs or whatever, but figure that the cantilevered table jostling down the road couldn't be good for the ribs/skin - and we certainly don't want to do that