I had one bitch that bred every other day for a week. We were thinking she was "early" (had only been 7 days since I first saw blood, but had to go out of town and it was the only time I had to drop off), we weren't really looking for a tie that day, but they did while we were standing and talking. She whelped total of 11 puppies. The other bitch I bred the "same time", both started the same time, 2nd bitch was bred Friday and Sunday, the end of the same week that the other was bred, only one pup, I think it was a little too early in her cycle. Both were done live cover, no prog test done, but breedings were done pretty much the same times that they had been done on prior heat cycles.
The bitch I just bred, did progesterone testing both cycles she has been bred, first time 3 years ago, she was ready day 10, this time wasn't ready until day 14-16. This one was done live cover, waiting to see how "successful" we were.