I have had my ham license since 1965, a period of 45 years (in 2010). In that time, my interests within ham radio have varied. In the beginning, you concentrate on learning the code so that you can get your license, then study some more so that you can get the Advanced license. Once you have accomplished these, then exam writing is over and you can do what you wish to do within the limits of the license.
One of my biggest interests in ham radio is DX. DX is looking for and working stations far away from you around the world. When I lived in London, Ontario, I put up a 48 foot tower, with a tri-band beam and tried to work the world. I made many contacts with this setup in the years that it was up. My first DX contact with this setup was into the Canal Zone. i have worked (i.e. had a contact with) over 100 countries as well, and well remember one afternoon working many stations on 15 meters when sunspot conditions were better. That was a great afternoon!. One other great memory from my DX days is going to Antigua on vacation in 1981 and operating from there. I borrowed a radio and 2-element beam from a fellow ham there and made many contacts during that week. What an eye-opener to be on the other end of a pile up!
One of my other interests now later in my ham life is QRP. With QRP, you use whatever receiver you like, but, to be considered a QRP contact, you must use 5 watts or less in transmit power. When you do this, your overall antenna system becomes much more important than if you are using more power. A lot has been and can be accomplished with QRP but you must realize that is not quite as easy as using more power.