Tube Rolling in my Pathos

I discovered the other day that the tubes in my Pathos Classic One MkIII were not the same brand...take break to watch any remaining credibility walk out the door...so with the help of someone on a Pathos group on FB I picked up some Mullard tubes.

I put the new-to-me tubes in last night and unexpectedly have been able to listen to music quite a bit today.  The Mullard tubes (that replaced a JJ and Audible Illusions combo) clearly resulted in a superior sound that is significant enough that the difference can be captured via iPhone video and heard through average earbuds.  I'm not saying that it's necessarily possible to evaluate which is better with the earbuds, but as unscientific as the two videos are I think there is an obvious difference.

Based on this experience and after reading multiple articles and forum posts over the years, what is your experience with tube rolling as it relates to the particular sound of a tube?  Here's a few specific questions:

(1) How much of a factor in the sound of a tube is its age?  How different would a brand new tube (once broken in) sound compared to an "identical" one that had been in use for several years?

(2) How much of a factor in the sound of a tube is its construction?  If I had two pairs of new "identical" tubes should I expect to hear any difference between the two pairs?

(3) How consistent is the characteristic sound of a tube?  How important is it to get tube recommendations from owners of similar/identical amplifiers?