I eventually put the OME HD (608 springs) front lift w/shocks on mine and it handles the extra weight of the bumper/winch much, much better now. In back I put a set of Timbren bumpstops and nisstec shackles on first hole because I still have my OEM rear shocks. http://timbren.com/active-off-road-bumpstops/
I would like to eventually replace the rear spring packs as they have sunk a bit and in general are just weeny but the timbrens make the ride much better with all my camping gear.
I had my bumper/winch with stock suspension for about 4 years (vehicle was less than 1yr old when installed) before I really noticed it sagging but by then it had dropped around 2".
It wasn't until after I upgraded the suspension that I felt I really should have done it sooner but the first year or two was fine with lots of wheeling and no problems.
Just depends on your $$ and what you want to do with your rig.