If you used the Meguiar's HD Headlight Restoration Kit it should have had a bottle of Headlight Protectant in it. This is an excellent UV screener but you'll still need to apply it every few months (takes quite literally a few seconds per lens to apply) since it will wear off due to all the tiny impacts it will get while driving down the road. The downside to restoring headlights is that the process removes what's left of the protective coating applied at the factory. But since the lenses have yellowed, most of that factory coating is already gone anyway. In any event, the restoration process removes what little bit is left and the lenses will now degrade faster than before. Using something like the Lamin-X kit is probably the very best way to go.