It depends on the service. Variables include disk design, corrosion resistance, number of cycles, and how to close the operating pressure is to the rupture disc set pressure. One approach is to ask the manufacturer for their recommendation. Typical practice for U.S. Department of Transportation vessels and discs is to replace them at the tube requalification (i.e., every 5 to 10 years in the U.S. depending on the retest method used). Unless there are specific reasons for frequent replacement, it's usually best not to replace discs too often since even replacing the discs potentially introduces risk. Reasons to replace the disks more frequently could include corrosion on the disk and fatigue from repeated pressure cycles. (The closer to the setpoint these are used—greater than 70-80%—the more fatigue and likelihood for premature failure).