1. once they reach the X block where you only get 25 Btc per payout, it would seem improbable that you would make a profit.
$ echo "4*365.25*24*6" | bc
210384
$ echo "8*365.25*24*6" | bc
420768
$
(the above numbers are once every 4 years, 365.25 days in a year, 24 hours in a day and 6 block every hour AKA one block every 10 minutes)
So after block number 210384 the Generation value will half to 25BTC per block. (circa 1 year 3 months from now)
And half again after block number 420768 to 12,5 BTC (circa 5 years 3 months from now)
But I'm inclined to agree with Gabi and nmat
1. No one really knows. Depends on a lot of stuff
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