CKC Studbooks Chart 1 How Many Litters for a Dam is Too Many?
The following chart, with statistics taken from the Canadian Kennel Club Studbooks between 2011-2015, shows that 8 litters within 5 years were born to this dam from a Canadian Havanese Kennel:

2011-2015 CKC Studbook Statistics
1 - 2010
1 - 2011
2 – 2012
(Note a singleton litter born 2/24/2012)
1-2013
2-2014
1-2015
This means that this dam was bred on almost every cycle over the five-year period under investigation.
It will be necessary to access the 2010 and 2016 Studbooks to get a more complete picture of these statistics. An updated chart will be posted when the 2016 CKC studbook is released.
International regulations:
Holland
The regulations in the Dutch Kennel Club can be found @ https://www.houdenvanhonden.nl/fokken-met-je-hond/basisreglement-welzijn-en-gezondheid/
Houden van honden
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Regels Basisreglement Welzijn & Gezondheid / Basic well-being and health rules
Section 4 states the following: Een teef mag niet meer worden gedekt na de dag waarop haar vijfde nest is geboren.
A bitch is not allowed to be mated anymore after her fifth litter.
United Kingdom
The regulations in the Kennel club can be found @
http://www.thekennelclub.org.uk/services/public/breed/restrictions.aspx?id=2058
In the UK/KC: 4 litters in a lifetime for a dam.
Canadian and American Regulations- CKC and AKC
Canadian Kennel Club - No policies in the policies and procedures bylaws for limiting numbers of litters in a lifetime for a dam:
https://www.ckc.ca/en/Files/Legal-Policy-and-Procedures/Bylaws_en
American Kennel Club - No policies on limiting number of litters over a lifetime for a dam:
http://www.akc.org/press-center/akc-syndicate/ask-akc/dogs-per-litter/
There are no regulations mandating number of litters in a lifetime for a dam in the CKC or the AKC.

The number of litters in a lifetime for a purebred dam is a basic well-being and health issue as noted in the Dutch rules.