Buying tubes 2nd Hand

looking for others experience on buying tubes from private parties. Seems like there is a lot of room to fudge on the age of a tubes when buying "NOS" tubes. Dealers tend to be fairly trustworthy but they charge a serious premium. How have your experinces via A-Gon or Ebay?
Just- I've purchased quite a few tubes off the web. There is always the possibility of getting a tube with less life than stated, but I try to stick with sources that actually measure the tubes and give the values per section. I also try to stay with sellers that have a good history. So far, no serious problems. Good luck.
I have purchased both NOS and used (test good) signal tubes from the following Ebay sellers. 1. K1dft and 2. Valves31. All tubes were of high quality (sound wise). If you are looking for tubes for a special application, I will suggest trying to contact them directly with your needs (at least they both made me this offer and I assume that they are open to this). It may take them a while to locate, sort and test the tubes, but everything worthwhile takes time. I have also purchased driver tubes for my amp on two occasions from Longplate @ this site which were VERY reasonably priced and which also sound excellent. He also has tubes that he does not get around to listing. The tubes that I generally buy (Amperex, Mullard & Philips MiniWatt 6922 types and Sylvania Gold Brand 5687's) are fairly easy to ID by the construction, labeling and etched codes (I prefer not the earliest, but the slightly later Amperex white labels with the "O" getter). If I were purchasing other types of tubes however, I would be lost as to dating them. I have seen some Amperex 6922 types on Ebay that do not look right to me, either the tube, the packaging or both (usually the packaging though), so caution is advised. Overall, I find used (test good) tubes to be by far the best bang for the buck, especially if you are experimenting with tube rolling. If I find a good deal on NOS that I am familiar with though, I don't pass them up.
Dekay, thanks for the advise, I purchased some from Valves31 via ebay using buy it now, based on your post. I emailed him to see what others he has. I am looking for some PQ or SQ 7308,6dj8 or 6922's so we will have to see what other stuff he has in stock.
Justlisten: What are you using them in and do you use matched pairs/quads or singles?
Very helpful information/advice, Dekay and Jctubes. Thanks for sharing. Another eBay seller I would recommend is Primotubes -- good quality, excellent packing, and responsive via e-mail. Can anyone recommend other specific sellers?

I use 4 matched for a Counterpoint Sa9 phono pre, a matched pair for an Audiologic DAC, and 4 per SF Power 3 mono amp. I have some singles (6dj8 Telefunken, Amperex 7308, a British made 6dj8 SQ, and another unnamed British 6dj8) which I just popped in the phono stage and it sounds better than 4 mathched Philips JAN 6dj8's that were in there before.
Boy, that's a slew of 6922's. I just use one at a time for the input tube on my amp and one 5687 for the driver (the amp has a volume pot). Because of this I can buy singles and the only matched tubes that I have picked up in quantity are Amperex White label 7308's (for a rainy day and a pair of Audion mono blocks if I can ever get around to them).