Locking out the OD ensures the trans won't keep bouncing back and forth between OD and whatever is your next lower gear. If you're on flat ground, it's fine to use OD. But not in the hills. Not sure if it works on your year, but on most transmissions with OD lockout, depressing that button also directs the trans to use a different shifting map which keeps the trans from upshifting until a higher rpm is achieved, ensuring the clutches are fully locked in most of the time. That is important when towing. The only thing you really have to remember is to keep revs above about 1800-2000 rpm when climbing, by remaining in whatever gear allows you to maintain that rpm. Your trans will likely do that for you, but it doesn't hurt to check it, especially on your first trip with that particular load.
2006 Jayco Seneca 34SS
2006 Jeep Wrangler Unlimited Rubicon Toad