I see lots of good ideas here.
However, for the past few years, I've been doing things a little differently.
I grow several varieties that are my favorite, and I save seeds and replant my heirloom and open-pollinated varieties from my own saved seeds. To make sure I get "pure" seeds, without cross pollination from other varieties in my garden, I do something completely different. Late in the season, I select which plant I want to get seeds from, and I take one or two sucker cuttings and root those in a smaller pot (12" or so usually). I grow a small clone of the plant indoors, in a sunny south facing window. I let that clone plant grow, blossom and fruit, and I gather the seeds from that clone that was grown indoors.
Sometimes I have a couple different varieties growing in different rooms. Other years, I'll do one variety mid summer, and another later on at the end of the season.
I typically gather seeds from only one or two varieties each year, and I have a good seed supply for 2 to 4 years after that.
This year, I'm starting seeds that I gathered in 2015, 2014, 2013, and for one variety, I still have seeds from 2012. I'll definitely be cloning/replenishing my seed stock on that one from 2012 again this year.
