I live in the mountians of NC and we have rain, snow, ice, wind and sun -- but I leave all of my 28 Piko/Pola structures out year round -- they have been out for 4 years now - without much UV damage. Previously these same building were out in the weather in San Diego for 5 years without any highly noticeble UV damage -- other than a slight fading of the colors which could be expected -- and which gave the buildings a slight 'weathered patina'.
Using the clear UV protection paints that are available will keep the color at a brighter level (for a while) but you will see them start to peel in a year or two ....
I would worry more about the glue/adhesive that you used to put together the buildings than the UV damage. - the glue that comes with the building kits is useless in high rain areas as is any type of Super Glue. What I have found that works best is to assemble the buildings using a generous amount of GOOP -Plumbing Adhesive on all seams.(get it at Lowes or Home Depot) Once that dries for at least 24 hours, I cover every seam on the inside of the building with a generous bead of Silicon Caulking (same that is used in bathrooms). Both of these products adhear well to the plastic but will also will flex, contract and expand when heated or cooled. -- if you don't do this you will find that in a season or two, you structures will start falling apart and will need to be re-glued.
Hope this helps
René
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