I rang up our rego office this morning and put the car, bike and two trailers onto seasonal registration since other than the bike don't get used all year.
The other side of this is since SA went to not issuing rego labels is that they're asking for plates to be returned 90 days after being out of rego. Their main reason being that someone might pinch your plates and use them in a crime. I doubt if it would matter to anyone looking for plates whether the vehicle is registered or not as they'd just take them anyway.
So being SA and supposedly cash poor I see it as a grab for cash. Return the plates and when you want to re-register then pay for another set later. They also charge an extra admin fee of $15 for updating expiry date and going onto seasonal rego avoids that little fee. It won't make much difference to the bike and trailer but the car really only gets used in the winter and I can't tow one trailer unless the car is registered. So 3 months rego every year makes sense for them.
https://www.sa.gov.au/topics/transport-travel-and-motoring/motoring/vehicles-and-registration/vehicle-registration/seasonal-registrationSeasonal registration caters for those situations where you only wish to use a vehicle for a part of the year. Examples of this may be a farm truck with a Gross Vehicle Mass (GVM) that is used during harvest, or a caravan used during the summer months.
Only the standard administration fee is payable providing the registration is renewed after 90 days and within 12 months of the previous expiry date.