Here is the way I think of it. But I could be way off.

Think of STEEM as the USD.

SMTs are goods and services. So if I own 10 shirts and 10 pants that would be the same as owning SMTs at the NY Times and Reddit.

What is the value of these SMTs is determined by the market. If you want to buy my 10 shirts we gage how much that will be based on the market.

So we get your question about the value of STEEM. You ask if it is a good long term investment. Well that probably depends on your plans with it.

Back to the USD. The USD gains and loses value all the time. If you are in America you don't really see this but let me give you an example.

If you wanted to buy something in Mexico 10 years ago it cost you about 10 pesos for each USD you wanted to spend (http://www.xe.com/currencycharts/?from=USD&to=MXN&view=10Y). Today that number is 18+. That means the USD has gained almost 100% value compared to the Mexican Peso. So if you wanted to retire in Mexico keeping your networth in USD would have increased your purchasing power almost 100% over the last 10 years.

Make sense?