The Nissan Path

I see just about everyone has the airbags in the rear..are they that good? My PF rides superb and doesn't sag (knok on wood) but I'm sure if I pile in 6 or 7 people it will get tough on the rear. I used to race a beautiful Buick Gnx at Atco and had the bags in the rear for launching but never in an suv. my Explorer had air shocks in the back, rode pretty good all in all when towing my waverunner..Maybe just firmer shocks will do..what's the firmest?..Monroe sensitrac are pretty stiff..are their zerk fittings front and rear for grease???