Agreed, restore check is essential, whatever the backup method, and my employer offers that as a managed service. But it's also hard to convince a non-technical, small business client to invest in best practice, unless they've already experienced a disaster first hand.
It is normally impassible due to time constraints to do a restore check after every backup. Even if time does permit you are going to effectively reduce the life of the tape by a half. What is important is to initially set-up and confirm that the appropriate backups work and can be recovered. Once this is done you can be fairly confident that backups are going to work (checking logs is important) however you must perform test recoveries to machines that can be made available for testing purposes on a regular basis as outlined in the company IT disaster recovery plan.
Don't have a company IT disaster recovery plan? Then you as the consultant or IT manager better arrange to have one implemented.