Preservation of data costs time and money, but so does reproducing it. You should therefore carefully consider what data needs to be kept and what can be discarded. Aspects to consider include:

• what is needed to validate findings in your thesis/publications?
• what might others conceivably find useful?
• how expensive will it be to reproduce?
• how expensive will it be to preserve?
• are you obliged to destroy anything?

How-to guide "Five steps to decide what data to keep" (DCC)