Hello MrsC2B, there's a lot on here about plastic greenhouses if you want to search for it. Never had one myself. From the posts on here it seems they will last til the first windy day, when the whole lot will blow away.
But maybe the people who have been happy don't post about it.
I'm sure the grapes who are happy with their plastic greenhouses will now let you know.

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From each according to his ability, to each according to his needs.