btrfs is in mainline now, and has a number of years to have settled down. Even if you don't like the more advanced features, it has some that tick all the boxes:
- good on-disk checksums to detect errors (incl bit rot) for metadata and data
- RAID modes to protect from whole disk failures
- realtime and online scrubbing to detect and recover from checksum failures from another copy (RAID1) or rebuilding from parity (RAID5/6) - no action required from user (contrast with PAR solutions proposed)
- subvolumes for segregation of data if needed, especially if there is a desire to consolidate multiple older drives and especially useful to pool capacity from these disparate sources to implement RAID modes.
- online reshaping for the above So, even if you're not accessing the data frequently, if OP cares about data I'm sure it's no hassle to plug them in once a year and let a scrub run (for a couple of days if needed, I know this part of the code is still terribly slow). Even if btrfs is deprecated today, it will be a long time before support is removed from the kernel, and even longer before the last distro stops supporting it, and longer yet before that last distro release refuses to boot on whatever incarnation of hardware is available to plug the drives into. All the while the data is free to be migrated onto new spare/surplus drives and a new filesystem if needed.