Do you have stock lights with condensation? After I painted mine, just once or twice, I had a little bit of condensation and it would go away very quickly, out the one way valve for condensation. That's what that funny piece of black "tape" is on the back of the light housing. If yours are painted already (meaning you split them and put them back together before) they could have condensation because you didn't seal them all the way. What you could do is unbolt the headlight from the truck, and just run a bigg bead of rtv, or windshield silicone around the outside where it goes together to make sure it's sealed. Also take the bulb holders out, and let the light air out, use a hairdryer or a heat gun to make it go a little faster, just get some warm air in the light itself.
Basically with the resealing, just make sure you use some kind of good OUTDOOR sealant, stuff that always stays pliable. Won't get stiff and/or crack.