CIC website says that to be eligible for PR you should have completed 2 yrs. of full-time employment as a live-in caregiver within 3 yrs. from the date you entered Canada under live-in caregiver program (
http://www.cic.gc.ca/english/information/applications/guides/5290E.asp).
If you are outside Canada for more than 1 yr. you would have to reapply under live-in caregiver program to re-enter Canada (
http://www.cic.gc.ca/english/information/faq/work/caregiver-faq14.asp).