Well for months i have been spraying my rubbers with wd40 and storing them in a sealed container, and keeps them fresh for months,
The reason for this is wd40 is a protector on rubber etc: mostly used to protect rubber and plastic on cars etc:

Well as it is also a water repelent i decided to spray my squeegee rubber with the wd40 shaked of the excess and cleaned the window wow fantastic slip been using it all day today and it has been fantastic!
so if you want extra slip just spray your squeegee rubber with the wd40 as and when you think you`ll need it,

cheers james