There have been many notable examples of countries which have risen from misery, and for which the stamps have followed suit. The three Axis powers of World War II - Germany, Japan, and Italy- were impoverished for years following their defeat, and stamps of those countries purchased during the lean years of recovery and reconstruction have risen considerably. Many of the countries of the Far East and South Asia were considered Third or Fourth World nations only a few decades ago, yet based on their recent growth, the time may come when Chinese or Indian parents tell their children to finish the food on their plates and pity the poor, starving Americans. Latin America, once a region dominated by corrupt, oligarchical dictatorships and American multi-nationals, has experienced a mega-trend of democratization and economic reforms which has created greater prosperity and a nascent middle-class where none existed before.
Of course, it is always possible that a stricken country will remain so for decades. When investing in stamps of such a country, the risk of loss may be minimized by investing in stamps which are sought by collectors outside of the country itself - extremely scarce to rare key items which are of interest to specialists, and scarce popular topical issues which appeal to collectors worldwide. Demand for such stamps will not be significantly affected should the country remain in the doghouse or even decline further, but will increase rapidly if it breaks out.