I do not recommend breeding a female until at least her third heat or at least 1 and 1/2 year old. Prior to this age she is still a pup and may have difficulty with delivery and taking care of her pups.
From that point I would skip at least one heat between breedings or breed her every year to year and a half.
I do not breed my females beyond the age of six or seven since they are large breeds and have a life expectancy of 9 to 12 years. Smaller breeds who have longer life expectancies can breed to a slightly older age depending on their health.
I hope this answers your question. Good luck.
I have never heard of that theory. Did a vet give you that advice?
A responsible breeder will give the female time for her body to recover from the previous litter. That would require her to skip at least one heat, if she comes into heat every six or seven months, and be bred not more than once per year.
I can only equate it to the human female mom. Would she want to be pregnant every nine months?
In the final analysis, I always consider the quality of life for my pets and even though I am a breeder. My dogs are my pets. They are not treated as livestock.
Good luck with your pooch and take good care of her!