I honestly dunno from UV protection, but LSPs provide a sacrificial layer that sure does *something* to prolong paint life.
When I had the Volvo still in its original ss paint, it was easy to see how well it was holding up- oxidation was obvious. The original owner never waxed it and you can imagine how it looked (even though it was always garaged)- chalky and white instead of its correct medium blue color. I got it, polished it out, and then kept it well waxed (#16 or Collinite) whereupon it stayed nice for *long* periods even though I kept it *outside* 24/7. Just a *tiny* bit of oxidation that I easily polished off with the Cyclo once a year.
FWIW, I experimented on said Volvo with BF sealant and some KSG, and they didn't seem to prevent oxidation nearly as well as the two waxes :nixweiss I quit using them as I was polishing those areas all the time and sure enough, they stayed nice a lot longer with #16/476S.
FWIW#2- The current owner is keeping it outside 24/7 in Memphis TN (hotter, more UV, etc.). It's not a fair comparison (with the above) as I had it repainted with b/c prior to giving it away, but with just 845 on it it's still holding up great for her years later.