i had the chance to test a few chinese made tube amp mentioned in this forum before ... indeed all passed my requirements but failed in front of my wife who likes to listen to real music equipment (e.g. piano, violin) and real orchestra show ... plus her favorable male singer (who yet to produce his own single album ... and the album having his the songs together with other artists are poorly produced and killed many tube amps ) ... she simply compared life performances against all amps ...
your question is too general ... tube amp reliability ... i believe ... is better to be found out by field testing ... i bought a few spare tubes for backup from different vendors of 淘宝... one of the tubes is found poor in quality but others okay ...
ha ha ... sorry i only took two photos ... i only need to buy 6c33c online (but subsequently note that a shop in hk also selling 6c33c) and other two driver tubes 6sn7 and 6sl7 are available in many tube selling shops in hk ... actually my preference is to test the new tubes before payment (using the tube testing machine, seen it in 5/f and sheung wan as well) if possible ...