What do you mean by "ageable"? Do you mean one that is made for long term storing over drinking quickly? Or the other way around?
If you want a lager that turns over quickly, the keys would be: low gravity (like maybe no more than 1.040), super healthy fermentation (plenty of yeast, plenty of oxygen at pitch), and maybe an additional clearing/fining agent (gelatin) before kegging.
If you are looking for long term storage, ANY lager you make will be better with an extra 4 months than when its first "drinkable". How long you can wait is a factor of your patience and/or pipeline.
Primary: American Pale Ale