Everybody that is considering spending money for data retention/conversion has to answer three questions:
- Am I legally required to keep the data?
- How much will it cost to convert and then maintain the data?
- How many of my customers will stop doing business with me if I ditch the data?

If the answer to #1 is “No”, then you need to do the math to determine a cost-benefit ratio based on #2 and #3.