how long does a dog need recover from a litter before they can have another one?

Answer 1

Dogs only come into heat twice a year.
The best,who breed for show and obedience, breed their animals once yearly-every other year.
Anymore often than this and the minerals and calcium are depleted from the breeding female, which leads to weak bones, early loss of teeth and early death.

Answer 2

YOU NEED TO SKIP ONE HEAT BETWEEN LITTER ,, DO NOT BREED MORE THEN ONCE A YEAR , And only 3 times in there life any more then that and you stress the dog to much and you will end up with sickly mother and pups