? Tube Replacement Question ?


As a novice in the world of vacuum tubes, I have a couple of basic questions. I have a Audio Research SP16 tube preamp I purchased new in January 2008 & use on a daily basis. The tubes have never been replaced.

(1) When is it prudent to replace the tubes?

(2) Will sound quality deteriorate with age?

(3) Are there advantages of replacing the tubes with aftermarket alternatives vs. OEM tubes?

Thank you kindly for your help.
kitjv
You will find it WELL WORTH the cost, to replace all the tubes with certified, "Low Noise" tubes. If you use the phono stage; they are a must, in that position. The higher the gain of the stage, the lower the noise necessary. If you are not using the phono stage, you won't notice any noise with older or noisy tubes, in that stage.
Considering all of the varied opinions & recommendations regarding aftermarket & NOS tubes, I am admittedly a bit reluctant to "tinker". Maybe this is my way of admitting that my audio system is more of a source of quality listening pleasure rather than an end in itself. Nevertheless, I appreciate Samujohn's point. When it comes to motorcycles & photography, some of my expenditures are hard to justify to the non-enthusiast.

I do not doubt that other tubes might very well be more pleasing to my ear. But I am unwilling to find out which ones they are by trial-and-error. It seems like there are too many variables that affect sonic quality to keep the risk of getting the "wrong" tubes low. Please correct me if thinking is unsound (pun intended).
"Only an expert reseller can tell who actually made a tube, or its condition.”

That’s also my opinion. Bargain hunting for tubes by the inexperienced is likely to turn out less satisfying and more costly in the long run. In addition to the variety and quality of tubes that they have in their inventory, the advise and integrity of the best resellers make it well worth the premium you pay. In fact, I would suggest that if one has a well set-up, high quality tube system, a call to one of these experts is almost requisite.
I recently owned the power amp, VS55 that matches your preamp. When I bought it I emailed Jim McShane and was very pleased with his prompt reply and his knowledge. I took him up on one of his suggestions and was very pleased with the results. My trade is law. I do tinker, but I also respect expertise. Especially when the one providing it is willing to explain and offer alternatives.
Rodman99999 makes the point that replacing all the tubes with certified low-noise tubes is "well worth the cost". Since I do not use the phono stage, is there an obvious difference in sonic quality will all low-noise tubes?