Well, the oxidation part is obvious. Don't let your beer get oxidized! Seriously though, there are ways to avoid most contact with oxygen. I've read some threads recently about using those carboy caps connected to CO2 and racking the beer with CO2 pressure, and with CO2 pumped into the receiving vessel as well. That brings your oxygen contact to almost nothing.
As for the hops, my understanding is that IPAs and such need to be drunk sooner rather than later because the hop flavor and especially aroma will fade over time. Everything I know says that the beers that age best are the ones that are least dependent on strong hop aroma and flavor, like barleywines and big belgians.