I believe each heat cycle where the female does not become pregnant somehow degrades the uterus but there are obvious risks with pregnancy as well as all the other reasons to breed or not breed, so I'm not sure if it's all that "beneficial". Whether or not the bitch is bred back to back would depend on the individual bitch and the breeding. For example, if the bitch bounced back after the previous litter, is a good mother, healthy, and say there's a limited opportunity to breed her to the stud that would be the best pairing, then I don't think the breeder should wait because of some arbitrary rule. But breeding back to back to back.... I don't know. I think most breeders who do a back to back breeding will then give the bitch some time off.
Liesje & the K9s
Nikon (GSD) U-CH SG Alta-Tollhaus Bono SchH1 KKL T1 FO PA TF-III FDCh-S CL1-R UJJ U-CA HIT TT CGC
Coke (All-American) VPC's Coca-Cola CGC, couch warmer extraordinaire
Indy (All-American) Blue Horizon's Indigo Girl, flyball star in training
Rainbow Bridge Kenya (GSD) U-CH Alta-Tollhaus-Krieger Lamb Chop CL1-R CL1-F RA HIT TDI TT CGC
vom Blauen Horizont / Blue Horizon GSDs