Just talking 2wd highway travel - not 4wd off-road. The 70 psi is still 10 psi short of max 80 psi at load rating of 1330 kgs per tyre, which is probably 300 odd kgs more per tyre than anyone would load their 4wd to?
With ~150mm sidewall, the less the pressure, the more the flexing, the more the heat build-up, the greater the potential for blow-outs. So, 7o psi on-road, around 45 psi off-road.
A recent 12,000kms trip up north on tyres with 40,000 kms already travelled saw no punctures or blow-outs. Mr Brown was loaded - 4,400 kgs so the back-end had no chance to get 'lively', and most of the trip was off-the-black. Did we have luck on our side or what!?