Do you buy burned-in output tubes?

[wintercept]

Hi all, I am shopping for a set of EL34's for my friend's VHT Pitbull Hundred/CL. In my previous work I have always purchased matched sets, but never ones with a previous "burn in" before matching. Randall Aiken offers a great and rational argument for burned in tubes at the bottom of this page, saying that since tubes change the most in their first several hours of operation, the burn in ensures a more stable match over the life of the tube. I have seen this argument other places as well.

Of the seller's I've used in the past, Viva Tubes does not specify a burn in period on their website (although I will email them to clarify), CE dist/Amplified Parts only offers "Apex Burn In" on JJ's (which I will also ask them about), and Tube Depot offers a 24-hour burn in @ $1.50 extra per tube. My sample size is small, but I have never had issues with any tubes from these vendors.

So as I try to form my own opinion, I figured I'd pop the question here because we got a lot of smart cookies here who I'd love to hear from. Do you buy burned-in output tubes? Why or why not? As I take on more tube amp work, should I insist on only using burned-in output tubes when it's time to replace, leave it up to the customer, or just leave it alone? Thanks!

 

[pbrommer]

I’ll offer my $0.01. Burn in is probably worth it. From my knowledge, it will help find the tube sets that “match” for certain idle current draw. It’ll also help weed out the tubes that are a bit weaker. Now, in ye olden days (so they say), people would grab one and drop it in.
Matching tubes is a very hot topic: some care a lot about precision; some are okay with a bit of mismatch. Me? I always had about 5-8mA difference on the one P/P I had.
So, enjoy these few shekels of knowledge, but I’m no expert.