All of the tube amps I've owned needed about 15 minutes to sound good. Is it getting better after that period? Perhaps, but I don't kill myself trying to notice any difference -- I just know it sounds good after 10-15 minutes. Solid state stuff takes a whole lot more time to warm up. I've fooled around with gear that sounds really disappointing until its been on for many hours if it has been off for some length of time. That is usually not a problem because the solid state stuff can be left on continuously.