I hope and I believe that your 'general rule of thumb' is not true (sorry, if I sound rude). This is just a myth. All CIC cares about is whether the sponsor is a resident of Canada. And the residency of Canadians is decided by the '183 day rule' (if you stay more than 183 days in a year, you are a resident!). As long you maintain your Canadian residency, you shall be fine. A sponsor doesn't need to worry and doesn't need to inform CIC about his/her travels.
I know this for certain because though I was a Canadian by birth, I have been a non-resident Canadian for most of my life. Currently, my work requires me to travel out of Canada almost every month and I had to spend about 2 months abroad in Dec-Jan due to my work. Hence, I had inquired about this in detail with CIC on their helpline, CRA and some other sources.