I find mine produce about two months and then wane.
I do a second planting at the end of June for more squash through the summer.

About six weeks is about the max that I can get from a summer squash. (from first picking to last)
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Well, you CAN get them to go a lot longer, but it takes a bit of work. Three things really do them in -- A) disease, especially powdery mildew; B) insects, squash borers and so forth; C) letting them go to seed, not picking soon enough.

So, if you spray them regularly with fungicides and insecticides, be really good about picking them all young, and keep them watered and fertilized, you can keep them producing a lot longer.

HOWEVER, it's actually a lot easier just to plant a couple of batches of them -- you can do an early one, started about a month before your last frost and transplanted, one planted just after the lost frost date, and another planting about end of June/1st of July.

Now,I used to do this some years. But frankly, we get kind of bored of them by late summer, and I've usually put up all I need by that time.

Also, in September, I will usually pick and use the small winter squash and pumpkins as summer squash, since they usually won't have enough time to make mature squash anyway.

I have never had a summer squash go all year long. Bugs or PM usually do it in at the end of July/early August.

In my garden, the summer squash do go all summer long. They start getting a bit of PM now when their leaves are so flourishing they hinder air circulation. But they still produce well. When nights get really cool and moist around Oct, they look raggedy and head to the compost bin. Sometimes they get pulled earlier to make room for the cool crop.

But our summer is dry and they're watered with drip irrigation. This way I've never had the need for fungicide nor pesticide. I can imaging in areas with high moisture, that may not be the case.

One thing I did notice is what denninmi said that they need fertilization and good watering. With inadequate nutrition and water, the leaves turn yellow and production decrease.

Mine usually last till I'm about burned out on eating them and my neighbors run inside and lock their doors when they see me coming with another sack of them.

my summer squash have been flowering for 3 months but not producing :( The zukes and cukes in the same box did fine...

My summer squashes do go all summer. They do get watered but not on the leaves. I do nothing to prevent mildew, the humidity here is low enough, I guess. When October rolls around the strength of the sunlight is just too low to keep them healthy and the powdery mildew takes over. Fighting it would be futile, their time has come.

I put the plants out as soon as it stops freezing. I start getting squash in August and the plants produce until it freezes.

So, not all summer, but certainly all season.