As you seem to understand, running new vs used has a few determining factors. Higher hp classes will want new tires as much as possible. Slower classes require them less, especially if the track is grippy. The other main factors are the kart itself and the chassis setup. Some karts get tight easily whereas others want more grip. My sr 206 kart likes new tires usually but I’ve been to tracks where I’ve ran the same ylc’s for three days against all new tires and won. Best thing to do is test it yourself. Midsummer I would be less likely to put on new.