In the longer term

In the long term everything is good. How long is the long term is the general "FAQ" for this term. My question is not that. This post is specifically related to investment in equity shares and the "long term".

They say, if you are a real 'investor' your investment horizon is bound to be "long term". In the long term, the returns are assured. But how is this "long term" measured? Is it with respect to our life spans or without any reference? So a question that comes to mind is "Are these assured returns in the "long term" going to be realised within our life spans?"

Consider a depression lasting for 60 years or more. If one is 40-45 years old at the start of such a depression, he/she will not last long to survive any such depression period. What about our "safe" long term then? Is it really safe? My question is exactly that: Is long term really safe?

Fuel...

For faster traffic, we are manipulating traffic flows by turning roads into one ways, banning a few (rather convenient) turns, diversions etc. Aren't we making people take longer routes resulting in accelerated fuel consumtion? Are we consuming the little of what is left of fuel rather too fast? Should private vehicles be banned and public transport be made mandatory? (At least till the time we find some alternative to conventional fuels...)

Sum total of living beings

The total energy in the universe remains constant. Does, in a similar way, the sum total of living beings remain constant? So can the rise in human population be explained by way of extinct species?

Souls...

If souls are immortal, are we over-populating the 'Soul-land' by over-populating earth? Or is that taken care of by re-births?