Super visa Vs Visitor visa for Parents

[H.B.]

Hi

My parents would like to get a visa so that they can visit us any time they want. They don't have any precise plan to visit at present though.

Is that recommendable to just apply and get the visa and then visit when ever they want.

Is there any condition if my parent get supervise or visitor visa then they have to visit to Canada immediately after getting the visa?

Thanks,