Yesterday I went out web-walking - mostly to read other people's blogs.  I came across Life in the Frogpond, and a post on it made earlier in the week by Becky of skinnyrabbit.com.  She was looking at vintage tennis sweater patterns, and offered up this one from a 1956 Bernat Handicrafter pattern leaflet (this scan is Becky's, but the original copyright on both pattern and image is held by Emile Bernat & Sons):

I collapsed into a pile of amusement, because my mother had knit this **exact** sweater for my uncle when he was a teenager, probably circa 1958 or so.   This sweater still exists!  I have it in my closet right now:

It's held up extremely well.  No excessive wear, weak spots or moth holes in the entire piece, although once natural color ecru wool has aged somewhat to a beige/light yellow, and somewhere along the line aggressive laundering seems to have migrated some of the dye from the blue stripes. 

Not only do I have the piece, I also have a photo of ME wearing it as a teen.  This is from my high school yearbook.  As you can tell from the wire frame glasses, nerd-bunch hair and wide shirt collar, was taken in the '70s:

Now that I've dated myself, I can also say that this 46-year old tennie is waiting for my own Tween-ager should she want to wear it when she's big enough.

Moral of the story:  Use good wool.  It lasts forever.