I would say so, yes. I've noticed the same thing with mine and have not had any problems with them... all I would say is make sure you have a decent amount of clearance behind the amp as the manual directs and keep that fan running.
Just let them burn man, thats what they are supposed to do. Those tubes being hot is what gives it such sweet tone, and with the 5 watt mode you can drive em' hard. Bring it to the point of melt down and enjoy the sweetness. BBBB