The way i see it - by the time it starts to decline you will have collected more than your fair share needed ; and while you may question the length of the investment you can always put the collected into a different basket - although it will take much more time for that second investment to grow it could also end up declining .
I think watching the market would also play an important factor ; buy low sell high - or trade in different cases .
I have ways in the game i play - with a fresh account and no money to my name ; spend 10 minites and gain 100k - then take that 100 thousand over a week and make well over a million .. While most players struggle to make even 50k in the course of a month .
I think its all in the way you see money ; if something gains money aquire it - when it declines trade it off for something that aquires more or something that holds its value overtime - when that is finished declining ; buy it all back ; by then you should be able to afford twice as much due to the price decline .