Hi PSL,
I haven't shared the same window problem you have. Mine seem to function ok - though a few scratches appeared on the quarter lights over the winter, which could be mechanically-caused. The Krytox came from:
GBR Technology, Unit 6 Jupiter House, Calleva Industrial Park, Aldermaston,
Reading, Berks, RG7 8NN
tel: 0118 9820567 fx 0118 9820590
Cost for 2x Krytox GPL105 30ml bottles/applicators £42.89 inc postage/vat
It lasts for ages, as it is used fairly sparingly.

Hope this is useful for you. I had the roof down this evening. Tomorrow's weather isn't promising, but the weekend is!!