On my truck, get much below 35-40, and the tires become 'squishy'.... and the rear of the truck kinda wallows around, especially in corners...... it's just too soft for my tastes, to maintain control.

 

That's a heck of an equation. Seems to work out well. When I first put my 285/75-16 BFGs on this truck I was running them at about 60 psi front and rear but noticed the middle wearing out after a few thousand miles. I found that 48 to 50 psi on the front and 28 to 32 psi in the rear made for even wear.
Like HeyYou said, it felt squishy at first. Once I got use to it I realized the truck was much more planted on both dirt and pavement. It also smoothed the ride considerably.
As for the tires, I'm pushing 30,000 hard miles on them now with clean, even wear (except for the rears starting to cup, needs shocks). They will get replaced this tax return if not sooner because I've gotten my use from them, but I've never had tires last more than 25,000 miles before this.

Edit: Forgot to add, if I know I'm going to be playing in the dirt all day I'll air down to 20-25 psi front and 15-20 psi rear. This smoothes out anything under 4 inches tall for me and give amazing traction in everything from snow to boulders.

 

Yeah I think I will just leave the rear a few psi above and rotate them regularly.