To be safe, get two Bitcoins.
lol i agree with this. in 20 years 2 bitcoin may be worth 2,000,000$ and to me a 2m retirement fund would last if you plan on retiring at 60 and living untill 75 or whatever. specially if you have another income coming in still from ssi or whatever it may be
safe side get 5
if it will peak to 2,000,000$ i`m fine with onl 0.5 btc
Indeed its simply just not possible, you have to keep dreaming but do not let your dream take over your mind.
Its also that its even the question if it ever will go higher than 1500 dollar...