The smartcard and USB-connector of the Nano have an augmented CC (Common Criteria version 3.1, part 1) certification level of Evaluation Assurance Level (EAL) 5+. This means an estimated lifespan of 30 years or 500.000 on-memry write cycles.
The Ledger Blue will be rated with CC EAL6+.
Source:
https://www.reddit.com/r/Bitcoin/comments/7202fi/comment/dnesz4a