First of all it's worth noting your asset lifecycle:
Asset Lifecycle diagram
So when a bike becomes post operational it goes to one of these states:
- transferred (to sales dept for example)
So you update the bike's status to reflect that. That way it will no longer be available to rent.
But its quick and easy to do.
THEN at the end of your season you're going to want to tidy up your spreadsheet so you don't have old bikes lying around. You do that by archiving off old bikes.