With the way he was talking to me about it he appears to know exactly what he's about to do and how its going to end for him. But for me his idea has left some apprehension and questioning in my head due to the length of years (good 16 years) he is going to keep up with. From my angle the years are too much as no one can certainly say for sure about what the future of cryptocurrency and bitcoin holds despite how positive it could be looking today.
Actually both a good thought in terms of investment but I will suggest and appreciate his idea as he wants to invest 20% of his salary every month. This strategy will help him to get more returns. But if you suggest to invest in every 4 years then he might miss the bullrun.
And we should keep trust on Bitcoin because mass adoption is ongoing and it's totally decentralized and transparent. And Bitcoin already proved about it's potential in 14 years by creating history again and again.