Questions from a Tube Preamp newbie

I think the Brimars are Kevins favorite. The smooth mids of mullard without high end roll off. Plus, cheaper than mullards

I wonder if the Brimars add more sparkle on the top end vs the JJ's. I hope not. I think the JJ's top end (and low end) is perfect. Just a little more silk on the mids would be nice.

I wouldn't use the term sparkle to describe the Brimars, I would say they have a nice amount of "air" in the highs, a very realistic sound. 
RCA Cleartops and Amperex have sparkle, meaning extended highs. Never tried JJs.

I used to be a "solid state bigot" but about a year ago replaced my solid state preamp with a tube model.
1.  How long do they last?  I suspect it depends on how much current is running thru them.  In my experience, tubes seem to start to sound "dull" in power amps after a year or so, but in preamps, last much longer, being that they don't flow so much current.  I have a friend whose preamp tubes are 8 or 9 years old.
2.  When I got my new tube preamp it seemed that the tubes seemed to "settle in" in about 100 hours of playing time.
3.  I replaced the stock tubes with Gold Lions, and I found the sound improved immediately, especially female vocals, acoustic piano and violin.  After the Gold Lions broke in, they sounded even better than the stock tubes.
4.  For the preamp I own, most people seem to enjoy the Gold Lions.  My preamp came new with JJ tubes and they were OK, but not as "musical" as the Gold Lions.

@ejr1953   Did you get your Gold Lions from Cryoset?