Partial agreement: almost any drive works best with not more than 50-70% utilization, but what I've dug up (e.g.: second hand info) suggests that minimizing rewrites (to an SSD) adds to longevity.

i.e., an SSD is best used as a tool to house executables you wish to load quickly, but not a great place to keep a swap nor as a data drive. See the reference to flash longevity in Re: OT: SSHDs Any experience?.