With most tube gear, you can expect a MUCH longer serviceable life than solid state gear. Most parts can be replaced on tube equipment while many solid state gear becomes unrepairable because a chip or transistor is no longer available. Also, tube gear has far less parts because the circuit is simple. One of the technicians at a local shop restored a solid state receiver as a labor of love. It took, among other things, replacing more than 200 capacitors; this would never be done as a commercial repair.
My tube preamp is about 15 years old and has required no repairs nor replacement of any tubes. Moreover, most of the parts were very old when it was built by a custom builder. The power supply is new, but the audio circuit parts are up to 80 years old.