Trimming them back is a great idea. It forces new stalks and flowers to shoot up and will make them stockier and more prolific bloomers in the long run. It's hard to cut off blooms, and will delay bloom time some, but you will be much happier in the long run.
As Tina says, trimming them back is probably a good idea. But you also need to make sure they are getting enough light. Snapdragons really want full sun.
Absolutely you can get them back! You can get them within an inch of their life...litterally...or you can even go 6" :). Both @Tina Hohman and @Douglas Hunt are spot on. Here where we are in zone 7b we can over winter them this way without distracting from our current planting. They become so much more beautiful when you give them a hair cut.
Yes, give them a good trim. Mine got lanky and stopped flowering for a while. I thought I was doing correctly by just pinching off the dead flowers, but once I really cut them back, they grew back vigorously.
Thank you all for responding to my question. I did it and I might even do more. I grew them from seed and I want to bermuda of them.