I have a temporary work visa and I wish to extend my stay in Canada beyond my visa expiration date. I understand I can apply for an extension as a visitor from within Canada? Can I do this even if I have had a temporary work visa beforehand? Can I apply for multiple consecutive visitoe visas?

If you hold a valid work permit (i.e. "work visa"), then you may seek renewal of such from within Canada or seek a change of terms to seek to stay as a temporary resident (visitor) alone. There is no specific bar to having more than one or consecutive visitor visas.