Dear ger56,
Normally no problem, being around 5% Less means tube life should increase with indirectly heated tubes, assuming a good design. Directly heated (thoriated tunsten filament) tubes are another matter, should be within 5% or closer rated voltage.
If the other voltages are decreased, plate dissapation is reduced, so again, generally, longer life. The only consequences would be lower output power in the output stages of an amp, signal voltage as a driver or phase splitter, and increased distortion, how much is determined by the component's design and what it is used for.
Preamps are generally less affected than amps as only a couple of volts RMS output are needed. If as a driver or phase splitter tube in an amp, then the max signal output voltage is reduced before clipping and the distortion rises. There might be exceptions to this rule, but the design would probably be somewhat of a compromise.
Hope this helps.
