I have found, both with my Yorkies and with the Pekes I owned in the past, that it's not uncommon for their heat cycles to be longer than 6 months in between. My Yorkies have always gone 8-10 mo between. Then again, sis has a female (pet only) that was going into heat every 3 months up until she was spayed at a little over 2 yrs old.
It has also been my experience that as they age, their heat cycles space out even more or become practically non-existant. Of course, ideally, they would be spayed when they are older, but...
I'm sure it varies. It will be interesting to see what others have experienced as well.
