I don't think winter tyres (ones that simply have a snow tread) wear out particularly quickly, they are just noisy and don't handle as well, but I do think that winter tyres made with soft rubber compounds as are being widely sold now do wear out quickly at higher ambient tempertures.

I don't know anything about the Avon tires, I don't think they are sold here.

I am familiar with the Pirelli tires you mention. That tire has been discontinued by Pirelli, and replaced with a newer generation tire that contains a more current rubber compound. I don't know how soft (if at all) the compound is in the discontinued tire, but probably not very soft given how many years ago it was designed.

I don't get my information from anecdotes, I rely more on technical publications. Pirelli themselves quote the 7C ambient temperature guideline on their website. They seem to accept it.

Pip pip, cheerio

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue