That would make your failure rate higher (from increased infant mortaility) and your maintenance more expensive (more spares, more transaction costs, more work,

That would make your failure rate higher (from increased infant mortaility) and your maintenance more expensive (more spares, more transaction costs, more work, replacing perfectly fine working parts too soon). Drives have on-condition monitoring via SMART so you can predict age related failure. Scheduled replacement is almost the worst maintenance policy.