your parents must be physically present in Canada for at least 730 days (2 years) in every 5-year period.
-sailor(Ocean & Mountain);
2017-4-19(#10747685@0)
One may be temporarily outside of Canada for a total of 212 days in any 12 month period and still maintain OHIP coverage as long as the primary place of residence is still in Ontario. However,
-sailor(Ocean & Mountain);
2017-4-19{53}(#10747776@0)
the ministry does have extended absence provisions.