It seems that some of the best pipes in the world are quite old .Is it because they are old ,that they are good and have in some way improved with age?
RORY
In fact, they’re not old. Paddy Keenan is 21. Paddy Moloney - 26. It’s the stress of tuning the instrument that causes premature aging. 
No
Uilliam
They say the Flat sets made in the 18th and 19th centuries by makers such as Coyne, Egan, Kenna etc have qualities in the internal workmanship that have since been lost and only now are makers beginning to rediscover them.
We can’t know if these pipes have improved with age because we weren’t around 200 years ago to hear them when they were brand new.
Cheers,
DavidG
We can only guess what the reeds sounded like, or were intended to sound like, as well.
djm
I don’t know about old instruments sounding better with age but there is one school of thought that some instruments improve with age. Or maybe they sound different.
I remember a conversation with a music professor when I was at university (I didn’t study music and it was a fair number of summers ago) and he was telling me about the pros and cons about ageing instruments. I can’t remember the conversation word for word but he mentioned that instruments left in cases do not mature/age. Instruments left out of boxes do. They don’t have to be played that much either.
Seemingly, if an instrument is left hanging on the wall et cetera it absorbs sound. In short it resonates. When it resonates the wood flexes and therefore “matures”. It builds memory. Not to particular notes of course (or maybe it does) but the wood is under tension because of the flexing which takes place. Similar to a reed I suppose. It has memory but if it is not flexed/played it becomes dull.
I can see some sense in this as we have a tenor mandola and a fiddle hung on the wall and when I play my pipes, certain notes resonate through the fiddle and tenor mandola. It can be heard as a type of freak harmonic.
Based on this I am inclined to believe what the old guy told me.
Whether or not many of the old sets have “matured” through exposure to either playing or sound absorbtion I cannot say. However, many of them do seem to possess a certain “tone”.
Joseph (the UK one) 
This has come up a couple of times before. Its true for stringed instruments, like fiddle, or the things on your wall (held up with large nails, hopefully), but that is because the wood vibrating makes or amplifies the sound (sound box). I don’t think anyone ever came up with any evidence or reasoning for this to apply to woodwinds like the UP chanter.
djm
I’ve heard this argument before as well. Perhaps it works to a certain degree, but sadly it appears that even the finest instruments have a “sell-by” date. I read an article somewhere recently about how the tone of an increasing number of Stradivarius instruments is apparently starting to take a dive. In the UP world, take note of the number of players who play Coyne or Kenna sets but have taken to playing modern copies of the chanter. In some cases, this may spring from a desire not to cause any undue risk to the original chanter while touring, etc. However, in some cases (perhaps through someone’s tampering decades earlier), the original may have developed quirks of some kind that are too frustrating to deal with.
They say the Flat sets made in the 18th and 19th centuries by makers such as Coyne, Egan, Kenna etc have qualities in the internal workmanship that have since been lost and only now are makers beginning to rediscover them.
We can’t know if these pipes have improved with age because we weren’t around 200 years ago to hear them when they were brand new.
Cheers,
DavidG
It was probably then, as it is now: A mix of sound quality. Even between sets by the same maker. I have found that it is a little like predicting earthquakes. You get famous for predicting one. Now, try to predict another, and another…
Cheers,
BC
(By the way, I’d be interested in knowing who “they” are.)
Perhaps Coyne and Harrington made some real stinkers. There were probably a lot of bad pipes from other makers, too.
The best pipes survived because people were willing to keep them going.
How many P-sets are going to be running in another fifty years?
Mukade