A printing apparatus and method to for use in a continuous high velocity mail production system, preferably for printing postal indicia. A transport path conveys a series of mail pieces at a print velocity. At least two ink jet print heads are available to perform printing operations. During normal operation, only one print head is operating at a time. To allow continuous uninterrupted operation, when a first print head is removed from service for a maintenance operation, a second print head is automatically brought into service. Adjustments to the triggering of the print cycle are made to account for the different print heads at different locations.