Well I posted my idea on here a year ago and the headlight is still clear . No sign of peeling , yellowing , etc . My car is not garaged either . So I guess its doing the trick .
Get clear gloss yacht varnish . In the can the varnish looks slightly golden , however once applied and dried it is crystal clear . Usually I dilute it with mineral turpentine so its quite liquid , then I use a lint free cloth ( like you use to clean glasses ) and apply it in linear strokes...
I use only one UV sealer for my headlight restoration and it applies easily and lasts extremely long time . .......Yacht varnish .
Highly UV , water , salt resistant . Also does not crack or peel . I love this stuff :)