creating feminized is a bit more complicated, however, if you have good F1's it is still worth it to make spare seeds for emergency and such. you can store pollen for months in a freezer, i can't really say how long, i have tried 4-5 months and it worked perfectly, i suspect that after a year or 2, well stored pollen will still be viable but thats a wild guess. to make pollen is actually quite simple, all you need is a closed box, doesnt have to be big, cut off several clones off any vegging male, i stick them sideways in a floral foam(oasis) block and place a cfl 12/12 above with a smooth glossy capture tray below, and i would turn off venting when i open the box for watering to prevent pollen flying around. the clones just root and produce pollen that easily falls in trays below and i scrape that into small vials into freezer in airtight box with sterilized rice inside to prevent moisture. i use a small paintbrush to pollinate the females, then spray with water an hour later to remove excess pollen. it has been a while, but i still have a batch of very good and very viable back crossed william's wonder seed, to 87.5% back crossing and really stable results that repeatedly impress me