2 Antminer U2's will never mine 1 btc in 7 months. More like 400 months.
If you start now, you will never get 0.02 BTC with 4 GH/s (2 * U2).
But, Chrithu could have been hashing for months already since the difficulty was much lower.
You can use a profit calculator to check your expected mining revenue and profits.
Yeah true hence I spoke out against buying any kind of asic now.
This maybe off-topic here now, but what I kind of speculate on is that the way mining works might be fundamentally rethought when devs see the decentralized nature of Bitcoin in danger, and then mining with lower hashrates might become more attractive again.