I'm actually quite impressed with how well they've kept. I picked them in October and it's now May. I had one that was starting to go bad a couple months ago but it was still good enough that I cooked it & added it to the dogs' dinner. I stored them under the buffet in the dining room. It's not near a heat vent, shielded from the sun and close enough to the kitchen that I remember to eat them!
If you'd like to see how they grew, check this link: Spaghetti Squash posts
I grew the Small Wonder variety of spaghetti squash. This is actually one of the smaller ones. It's little enough that I can eat it myself. While I normally have no trouble eating leftovers, when I tried leftover spaghetti squash, I wasn't very happy with it. I'd recommend only cooking half the squash if it's too big to eat at once. Scoop the seeds from the second half, wrap it & pop it in the fridge for another day or so.
Rinse the squash if needed and carefully cut it in half. Be sure to keep track of all your fingers, sometimes the squash are not the easiest to cut.
Scoop out the seeds (which you can cook and eat like pumpkin seeds if you want to) and place in a microwave safe dish. Microwave on high until soft enough to dent when pressed. I'll recommend a knife handle for this task though I often use my fingertip for this (and soon regret it). This little guy took about 9 minutes to cook.
Once cooked, I let it cool a few minutes then holding the skin with a towel, I scrape the stands out with a fork. Then add a little butter, garlic, salt & pepper & Parmesan cheese.
Top it off with a sprinkling of mozzarella.
Then bake until the cheese starts to brown.
I'll admit, this may not actually be the prettiest I've ever cooked- I used the toaster oven and then left it in a touch too long (I was chatting with hubby on Skype). It was still pretty tasty though!