Replacing the entire set of 32 tubes on the GM200 costs an extremely reasonable 500 Euro for a matched set from the factory (you really want to order them from the factory as close matching is absolutely necessary). This is hardly expensive, especially when considering that these tubes have a 10,000 hour lifetime. With idle power consumption of about 1000w this is not an amp that you leave on all the time so, assuming that you use the amp for 2 hours a day, every day, the tubes will last for 14 years. Spare sets can be ordered from the new distributor, Audio Analog in Italy.
The capacitors are relatively cheap to replace but if you are worried about heat affecting the capacitors, use the tube covers that Graaf supplies. The amp is not quite as pretty with them on as it is with rows of exposed glowing tubes (although it remains a truly stunning looking amp) but Graaf is effectively doing the same thing as Porsche does with its Turbo cars - Porsche puts a thin dimpled aluminum heat shield in the 1" space between the exhaust and the very thin rear plastic bumper to stop the extremely hot exhaust from melting holes in the bumper). The tube covers protect the capacitors and transformers from heat damage in a similar way. In fact, in addition to the covers acting as a heat shield, air convection currents will pull in cold air into the bottom holes on the covers and hot air will exit through the top, cooling things down even further on the rest of the amp. A bit counter intuitive - you would think that putting the tube covers on would make things hotter but they don't.
The capacitors are relatively cheap to replace but if you are worried about heat affecting the capacitors, use the tube covers that Graaf supplies. The amp is not quite as pretty with them on as it is with rows of exposed glowing tubes (although it remains a truly stunning looking amp) but Graaf is effectively doing the same thing as Porsche does with its Turbo cars - Porsche puts a thin dimpled aluminum heat shield in the 1" space between the exhaust and the very thin rear plastic bumper to stop the extremely hot exhaust from melting holes in the bumper). The tube covers protect the capacitors and transformers from heat damage in a similar way. In fact, in addition to the covers acting as a heat shield, air convection currents will pull in cold air into the bottom holes on the covers and hot air will exit through the top, cooling things down even further on the rest of the amp. A bit counter intuitive - you would think that putting the tube covers on would make things hotter but they don't.