Delivery terms are an important part of the agreement. The contract should specify exactly how the images are to be delivered. If they’re online, the minimum time should be specified exactly as people are point out. Other times it is a thumb drive included along with the prints.

For online delivery giving notice before they’re gone and keeping an offline copy are commonplace, but not mandatory unless they’re specified in the contract.

The contract is everything. Don’t wing it because you cannot replace or redo a bad contract, and that’s usually only discovered after someone takes the photographer to court; work with a lawyer comfortable in the field to help you make a good one.