are your plants in the open air or in a greenhouse? if they are in the open then bees should be able to find male flowers on other nearby plants and pollinate yours.
as for how long pollen lasts depends on lots of factors but you have nothing to loose in trying.

Thanks Eileen. Yes, they are open air plants & they need full sun and lots of water, preferably rain water - it affects the taste.

There should be dozens of flowers open at a time, every day, on each plant, so at least some in the group should have males opening. Unless the plants are very puny, my best recommendation is to look harder.
That, unfortunately, sounds a lot harsher than I intended, but I have found through personal experience that squash blossoms can be very hard to locate, tucked under the leaves as they are. I have had my squashes refuse to produce female flowers, because it was too hot, but never the entire patch synchronized in opening different genders in alternate days.

The way I get daylilies to go to the next day is pick it and put it in some water. I let it sit for about an hour and then put the flower with the water in the refrigerator. The next day, I let it sit in the sun for about 30-60 minutes, and then use it. I would trim the flower part off so just the anthers are there with the pollen. Worth a try.

Thanks Tug. I only have 1 single squash plant. It's all I have space for, but it's got runners in all directions. The blossoms are easy to spot, gargantuan yellow blossoms about 10" diameter. A tiny squash is attached to the female blossoms. We are still early in the season. Maybe as it matures it will produce male & female blossoms simultaneously.

Oh, I understand that! They are rampant! I've always grown two or three at a time--and scrambled for room--because cross pollination is better. I guess that alternating genders on one plant is plausible, because the plant really wants to be cross pollinated. From what I learned in college about pollen storage, I would try putting the pollen on a small square of clean rag paper, fold the edges in to make an envelope, tape it shut, and put it in the refrigerator. When the female flowers open, take the pollen out of the fridge, let it warm up for 15 minutes or so, and then apply with a swab.
Here in the desert, the flowers are half the size, and hide under the leaves--probably our low humidity and ferocious sunlight. I try to hide, too! :)

Might it help to get some pollen on a small brush and keep it carefully until you have a suitable flower to try it on.

Thanks. I will give it a try. I had one developing squash but the squirrels got it. lol. oh well. Hopefully there will be more.