I'm running four of the three jack style jacks on my camper. It came that way to me. It's more stable this way, but still nothing like the new jacks that mount solidly to the corners. My take on it is that three jacks works well with one person, while having four works good with two people cranking. When I do an offload by myself, I run from jack to jack to jack, going 10 cranks (~1/4") on each one. That's a lot of running! When I have a friend, we go about 20 cranks on the front, then on the rear, then the front... Much faster!!
As for stability, I don't feel comfortable leaving the camper on the two bolt removable jacks. Even with four it's pretty wobbly. As I said before, the new ones that bolt to the corners are what you want if that's what you're after.
Honestly, if your mounting points are iffy, I'd just swap the jacks from side to side, so you're getting three fresh mounting points and then just enjoy your camper! I rebuilt my corners and it was NOT FUN.
C