10 -15 million ti invest it bitcoin? you dont know how much much the price for bitcoin in the next few years and still you invest it like alot of them. It just wasting you money. If I were you, I sure make a useful things with that money and no need to spend it like this. Nope the millionaires didnt do the same as you did. They will plant everthing very cautious
Satoshi didnt sold his bitcoin, and i`m sure he is a multi millionaire, if not almost billionaire. So i`m sure most millionaires do the same.
C`mon i`ve seen videos on youtube, miners bought ferraris. Of course they spent their fortune, but i`m also sure they kept a few ten-thousand bitcoins just in case it will go much higher, besides they are comitted to bitcoin.
Otherwise, diversification is the best, i would have invested that money in other things too not just bitcoin, in case bitcoin collapses (very unlikely)