High speed recording means drive is using a higher power in the pick up head to "burn" pits on the recording layer of the disc. The recording layer is made of organic dye. Media like Taiyo Yuden, MCC uses mixture of 2 azo dyes (1 to cover high speed region, the other to cover low speed region). Ritek on the other hand uses mixture of 5 dyes (including azo, cyanine and possibly styryl). Possibly Ritek is trying to save money (100% azo is very expensive) while not sacrifising too much quality. As for Princo, it is mixture of cyanine dyes.
Cyanine dyes are known to require much higher power than azo dyes. Styryl dyes can not be used along, but when used together with other dye, they present effect of reducing the writing power.
My suggestion is not to burn 8x too often with media that require high recording power. Nil's 1.10 is a gift from heaven, but if used too often for high power media, the pick-up head might deteriorate. Pretty soon, you might not even be able to brun 8x for those certified media.