First Watt F5v2 needs to heat up?

Loving my F5v2.....But one thing I notice is it needs to play for at least 1/2 hour to really start sounding good. Is this me or is this a reality? My VTA Dynaco ST120 needs about 45 minutes before it starts to sound good, but we are talking tubes and I get that they need to heat up. But a SS amp needing to "Heat Up"?......My Sound Artist SA200ia and my Yamaha M45 sound great the second you turn them on.......Psychoacoustics???