Philately is just not only a hobby. But this is kind of investment in the future. An old stamps become valuable thing when it almost difficult to find. And it become rarely. There are some stamps with expensive price. And most of them was very old stamp. Like: The Three-Skilling Yellow, The first two Mauritius, The inverted Jenny,
British Guiana One Cent Black on Magenta, U.S. Franklin Z-Grill, and Hawaiian Missionaries. Most of them sold hundred thousand dollar until million dollar. So start to keep your stamp right now. I hope it become valuable someday.