And I have never heard of any problem with the Rhea. I own an Aesthetix Io and have not had a bit of trouble with tubes over the three years I've been using it. The Rhea uses similar topology for the audio circuit and a similar power supply design.
Tphalieros, the reports you say you've heard sound suspect to me. I follow these forums for analogue pretty closely and I've not seen any such reports about the Rhea in the forums. One consideration: like the Io, the Rhea generates a lot of gain. Those first gain stage tubes are critical for low noise. People who routinely roll a vintage tube into those locations are asking for trouble unless those tubes have been very carefully selected.