I know periods in the past have been very good as stamps became a fashionable investment when people realised some enormous increases in value. Then people thought that could be repeated by hording sheets of recent issues expecting some reasonable increases in time, and sadly failed miserably and therefore killed stamps as an investment strategy.
But time has moved on and there are still some issues of stamps that regularly increase in value.
But I wonder if this will eventually die out as the generations of old philatelists die out. There are other good reasons why this might be the case.
As it is unfashionable now and has been for a long time, can that mean there is room for some great profits if some form of investment in stamps refashions itself.