For me the answer lies in the type of seed.
For example, I never keep parsnips longer than a year, or onion seed for longer than 3. They just really lose vigor after that.
One of the things I try to do with corn and beans, when they get to be ridiculous is to eat some of them down to a manageable number. You can use onions and radishes as sprouts.
Some things don't languish long in the freezer, some things don't get used all that often. I'm having a drought year, so I'm being very careful with what I plant. That said, I've carefully sorted out seed of things I know were drought tolerant.
It really helps to make a note of weather on your seed packets. For example, if I have 3 packages of saved Cherokee Green tomatoes, noting that one was from an especially hot year, I may plant that one during a drought season. It also helps to make note of WHEN (early or late) that you harvested seed from something and compare these in the future. For example, gee did I actually save seed from something that bolts early in my garden? Great, lets plant it during a cold wet season. Harvested late? Great, let's plant that during a drought season, maybe it will hold on.
Too many squash? Try dividing up your seed among 10 packets, keep 2 or 3, and send an entire squash collection to someone else on the board.
Keep an eye on what others are experimenting with and mail out a chunk of seeds.
When I do a trial, sometimes I set aside what produced really well for me and send the others on to someone, someplace where they might do better. Or, someone who's fiddling with a project. Many folks here have generously sent me a pack of carrots or onions for my trials. Of these some did great here, others not so great. I've tried to send lots of carrots back out. But I still have many in the seed fridge. Okay so their biennial so that means I don't have to save carrot seed for maybe 3 more years.
A few years ago, Joseph sent me radishes and turnips. I planted a few of them over a couple of years and then last week I got a wild hair and said, "I wonder how Joseph's turnips and radishes will do in this drought?" Sometimes seed planting is a matter of intellectual curiosity.
I have found several seed library's that will take anything I know I'm never going to use again....like the squash that makes 50 pound whoppers. Sounds great until you have to lift them, and then they don't fit on the shelves. So the Richmond Library received all my GIANT squash.
Don't tell Dar, I'm also planning the same thing with Giant Watermelon. Bigger is not always better. Of course smaller isn't either!
Somethings I don't even bother saving seeds of, like Romanesco zukes. Why? I have 30 seeds in the freezer, that's enough of that variety for 5 years.
I do worry about some seeds though. I have enough tomatoes to try new ones for about 5 years...without even replanting the old ones. But hey, I like some of the old ones!
I got a Palmwoods tomato from Raymundo. On it, he noted the seeds were old. When I planted it this year, I double sowed them. And very few of those came up. (I've got 3!) Now, if he hadn't told me, I might have dawdled and never gotten any of them. I have a few more from Dr. Male & Dr. Dar to deal with next year. Some years its hard to choose!
I think there's choice #4, the seeds manage me