Can I overwork my dogs on pigeons and develope problems with/on Quail.

Yes!

Especially if you are using launchers.

Use a Higgins releaser will eliminate that problem

I've seen them get clingy when overworked on pigeons or with too much whoa.

so how much is too much?

I've seen dogs start to flag and even blink birds when overused on pigeons or any pen raised birds.

As long as you shoot a bird for them every so often, I haven't had a problem working them on pigeons. I know you don't want to shoot your homers, but catch a few wild ones to use as shooters.

When they get sticky and start pointing the launchers.

Pigeons are for breaking puppies/real young dogs to steady up. Once you advance to quail/pheasant/chucker/hun, I would not continue fooling around with pigeons with the pup. There will be nothing good that comes out of messing with a pigeon from that point. Pup will get too close and he will think the same with quail. You know what happens next. I think too much pigeon work will make pups more sloppy in their work and more lackadaisical i.e blinking or flagging. Pigeons have their place in my program, but not for long.

Pigeons are ideal for training stop to flush. They get up and out of site when launched. You don't want birds flying a short distance and landing in your training field. Then you don't know exactly where there located when your working your dogs

NTX is right on