I'm in zone 5 and my snaps bloomed all summer with deadheading. Just don't let them go to seed and you should be fine.

Tracy

i absolutely love snapdragons....so pretty and good in arrangements....they love the coolness of spring..and bloom the best then ......our kansas summers are hard on them..they dont produce the best flowers....but hang in there....when it cools again close to the fall....they bloom better again.i try to keep mine deadheaded also.

my snap dragon can't handle the hot climates in the desert in sunny california..

Snaps are cool loving plants, here in Alabama they live all through winter though dont bloom then. They start blooms in march and bloom well into summer, but as it heats up in mid summer, they slow down or stop blooming.

My summers don't get as hot for as long as down south and out west, but mine do bloom all summer. When they start getting too tall, I start pinching the stems back. Not all at once though. I pinch them just below the bottom flower that's bloomed. You'll be taking a few buds off at the top, but pinching them will make them branch out. More flowers that way and they don't get leggy. Just deadheading the flowers and not pinching the stalk will still get you more flowers, but I like pinching the stalks down better.
Enjoy!

Kat