OK, well break it down into steps.
First you have to leave when your Temp. Visa expires. You know when that is.
Second, you have to apply for a new Temp. Visa. I don't know whether you can do that from within Canada or not. Have you inquired through CIC?
If not, then you will have to re-apply from the US and wait for the visa. How long did you have to wait for the first one? Presumably the time would be the same again assuming they give you one.
I have to think that after doing this a few times someone somewhere will twig that you keep asking for another one and will start asking some questions.
I don't think this is a long term solution to your problem.