The grease zerks are one of the few parts that can, and do, get damaged. If they are screwed in too far and don't leave enough play for the bars to move they will get bent and/or break off in the head. $30 isn't that bad for peace of mind.
We were camping for a weekend back in Fall of 2012 and got ready to pack up on a Sunday afternoon and the right jack tube stripped out. Nut on top turned and turned but applied no lifting action to the spring bar.
I've seen this happen twice (on different Hensleys). Both times it was a little hex screw that had come loose. There is a little hole near the top of the jack screw tube to access it. If it comes loose and falls out you can usually find it stuck in the grease inside the jack tube.