I like to shoot target loads for about 75% of a shooting session. Usually I'll start off with a bit of buck shot or slugs to remember "this is what it feels like". Then I'll step down to target loads for a while... then finish up with buck/slugs again.
Also, I recommend playing around with making your own wax slugs. You can make some utterly devastating rounds out of some cheap 7 shot target loads with a little parafin wax. They're very easy to make, too. Check around on YouTube. These are one of my favorite loads to shoot when I'm just dinking around in the desert shooting milk jugs and bottles full of water.