FDC are safest investment except some 1948 Gandhi FDC from India. All other private FDC(without cachet or special cancellation issued for that day) and cachet less envelope are useless (such as First day Cover with Gandhi stamp withNepal Indian Embassy cancellation.!! )
But looks like it's not for investment, but of course for knowledge how to increase price by shill bidding, how to cheat, how to forged without getting caught etc.!!
To me it's does not justify to keep this PAPER for 40+ years and with all this deflation in money and all headache of storing it in a good place with good quality of album just get you negative return on investment.
But I think in future it will come down as there will be no new collectors are coming in to this hobby.
Not sure what is the future of Gandhi Stamps and Philatelic material, but to me it looks it will end up with other philatelic value. (which has NONE.!!)
In past we saw some very low value of 1969 Gandhi FDC from India with all 4 Gandhi stamps. In december 2011 it was only sold for 39 cents (0.39$). Yes only 39 US cents.!!
After looking 1969 Mexico Gandhi FDC price and 1969 Gandhi FDC from India, don't you think that Gandhi stamps and philatelic collection is in very DEEP TROUBLE.!!!!!!
Not sure about you but I think it's indeed in trouble. Still not sure read my following my blog posts to understand what is going on stamp collecting world specially in Indian Philatelic material with 1948 Gandhi stamps.
2) 1948 Gandhi Stamps: Are False hope of Riches - Part II ?
3) 1948 Gandhi Mourning Private FDC : Are False hope of Riches - Part III?
4) 1948 Expensive Gandhi FDC : Are False hope of Riches - Part IV?
5) 1948 Gandhi Stamps Early Usage cover : Gandhi Stamps Are False hope of Riches - Part V?
6) Maxi Card sold for $5100 with 1948 Gandhi Stamps - False hope of Riches - Part VI?
7) Indian Philately Exposed
8) Indian Philately Exposed - Part II