It seems like breeding questions are popular. Here's another one.
I have two yorkies, the female is almost four and the male almost two. They have had two very successful litters of puppies no health problems from parents or puppies. They have sold asap and I have had several request from people wishing to purchase a puppy from me. My question is should I allow these two dogs to bread at will or should I space the breeding apart? Thank's for the help.
Definitely don't breed at every opportunity. Pregnancy and nursing take their toll on a dog's body, and breeding too frequently can adversely affect their health. Without proper rest, the body may not be able to handle another pregnancy and you may increase the risk to the mother and puppies.
I normally recommend breeding no more often than every other heat cycle. That means breed on one heat cycle, rest her on the next one, and then breed on the one after that. You can wait longer between cycles, but I wouldn't do it sooner. Keep in mind that your bitch is a living creature, and not simply a puppy factory. You shouldn't let market demand force you to breed her more frequently than is healthy.
Also keep in mind my previous discussions about whether or not you should breed in the first place. Just because the parents are healthy doesn't mean that they're good breeding quality.