Another concern, apart from the risk to cathodes, is that of turn-on surge. If you turn on the HT quickly, by using SS diode rectifiers, the tubes are not yet heated and cannot conduct. There will be no current drain on the PS due to the tubes in the amp, so all the current through the rectifiers ia available to charging the smoothing and reservoir caps. This gives a great surge through the caps and some people think that's bad.
The remedy is to use a delay and a soft start, i.e. let the tubes get hot first, then allow the HT to build slowly. This can be achieved by using thermionic indirectly heated rectifiers, which can take up to half a minute before they start conducting, depending on type, and turn on quite slowly. This solution avoids the turn-on surge and also deals with any risk of cathode stripping, either real or imagined. It also results in a relatively
"clean" HT, free from SS diode "hash".
To minimize the impedance which is incurred with thermionic rectifiers, with the resulting voltage drop and "sag", thermionic TV damper diodes can be used. These have a long warm-up time and are quite rugged. They work well in either a "full-wave" circuit (center-tapped power transformer secondary) or in a Gratez hybid bridge, in which they make up the positive-going half of the bridge and SS diodes make up the negative-going half. TV damper diodes tolerate high PIV, high currents and usually high heater-to-cathode voltages.