100Gbase-LR for short range - how quickly will these get damaged? Advice on optical attenuators?

We're using 100Gbase-LR's for connectivity within a rack, or across adjoining racks (1.0 to 5.0 metres).

Yes, I know LR is overkill - but these are the optics I have access to, and we do need 100Gb. (This is for a Ceph cluster).

I've been told that at such short ranges, the high power can actually permanently destroy optics over time.

1. What is the mechanism by which this damage occurs? How quickly will the optics wear out? (i.e. hours vs weeks vs months)
2. For anybody that's used 100Gbase-LR over such short ranges - what steps did you take to mitigate this damage?
   I've been told I should be looking into optical attenuators, and clipping these on. Anything else?
3. Is there much variance in the quality of optical attenuators? E.g. Cheap from fs.com, versus a more reputable place like FIS. And what sort of DB rating should I be looking for?
4. Are 10Gbase-LR optics immune to this damage, even at short ranges?