Can you find someone who you won't destroy come Spring, just to be rid of them? Can you build a relationship strong enough to survive the bleak winter months, like a store of acorns put away against the cold, that will still let you be free when Spring arrives? I suspect it's likely, but would take careful work on your part, and a clear understanding of what it is you want. (This last might be the hard part)

Of course, I'm not entirely sure what "free" means to you poly people, nor what tied down means; if the person behaves as if they have no exclusive claim on your heart, then the only bonds are ones you are making yourself. Or maybe that's a naive perspective.

You're not alone in your summer/winter cycle; there's a reason for songs like The Lusty Month of May. You just seem to have more opportunity to express it than most, for which I'm both slightly saddened and slightly envious. :-P