All pianos benefit from being in very stable environments, not too dry, not humid, and a static temperature. This will help to keep it in tune for longer. Realize though that playing the instrument will knock it out of tune and the more you play the faster it will happen. Also, if the pin block is shot, it will go out of tune fast no matter what you do, because the tuning pins will slip. Additionally, regular tunings will help keep it in tune longer. I know that sounds a bit silly but it's true. If you wait until the piano is REALLY out of tune, the tuner will have to move the pitch farther which will stretch the strings and make them less stable.
In short the best thing to do is control the environment, and get it tuned regularly, twice a year is enough for most pianos. There isn't really anything else you can do to keep it in tune longer.
Also, do NOT oil the strings. This is the quickest route to spending tons of money to replace the strings.