The headphones need to play music to break in. Otherwise they don't move, like they were unplugged on a shelf somewhere. Plus, the output caps will break in the same time. You have to play music through them to get the cap break in.
I have left my tubes on for days without any problems. Then I have a dog and two cats, no children in the house (certainly not at my age!). The tubes get to their best sound 15-30 minutes after turn on. The don't sound as good cold, just after turn on. So a four day burn in won't hurt a thing.
And how long is 5000 hours anyway?
