the Seagull website has this to say about cedar vs spruce tops and aging...

"Cedar Top or Spruce Top?
We are often asked to recommend one of these tops over the other. Both Cedar and Spruce share the same virtues in terms of better sound and the ability to age. In the end, this is a totally subjective question that can only be answered by playing the guitars."

"Aging
How about this? You buy a new TV and its great but it keeps getting better the more you watch it! Okay, that's not likely to happen with your TV but it will happen with your solid top guitar. A solid top vibrates much more freely than a laminated (plywood) top. This results in richer tone, better dynamic range and better balance of tone. Not only does a solid top sound better initially, over time the vibrations from playing the guitar result in the top vibrating more and more freely. This phenomenon is called 'aging' which means that the more the guitar is played, the better the guitar will sound. It is important to remember in order for a guitar to age it must be played. A guitar left in its case for 5 years will get older, but it will not 'age'."

The url in case you wanna read the whole page is

http://www.seagullguitars.com/seagullstory.htm

;-)