Imho 6 years are way too long for use of tires, and if they last that long due little driving .. i'd probably sell them off after 4th year and use that money to partially recoup cost of news.
That aside, PS4 are nice tires, have lot of grip, are quiet, have immense wet grip .. but they are more street oriented then PSS, thus it's quicker to hit their limits when you overheat them on track. Then again, if your tire set lasted 6 years, i doubt you drive on track too, as then probably tire hardly would last one season
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