If the pollen is well dried and kept dry, it should last for weeks to even months if refrigerated. However, when crossing the purple and yellow forms, the yellow is always used as the pollen parent. If the two parents are the pure species, it may not work. However, if the purple form has some flavicarpa in its makeup, it possibly will work, so you should give it a go and see what happens.

Here is a link that might be useful: More about yellow and purple maracujas

Thanks for the Link kiwinut, I'll keep you all up to date with this...
NC