Thank you!! Glad to be aboard.
There used to be a member over at LPF (IgorT) that would test longevity, but he has gone missing for some time now.
From what I've gathered over time is that tuned efficiency, and not setting it on a knee bend in the graph will keep any diode running for a very long time. Good heat sinking should be enough if you dont push the diode too much.
IMHO running the 520s at ~260-280mA would be the sweet spot. Obviously a more efficient diode could handle a little more.