Typically you should spend at least 6 months out of Canada. A supervisa is a visitor visa so you are expected to return to your home and reestablish your ties again.
There's no black and white answer to this question so you're not going to find one. Ultimately the CBSA officer decides how long someone is going to be allowed back into Canada. Generally speaking, you want to avoid giving the impression that someone has permanently moved to Canada on a super visa. So if someone has spent 2 years straight in Canada, ideally they return home for a year or so before returning for another 2 year visit.
Hi, sorry but a bit different question. Do your parents have a super visa? What is written in the visa category in the visa counterfoil on their passports?
Is it 'PG-1 visitor visa' or 'Visitor visa'?