I don't think I agree with your concept in saying that we need only discretionary income to invest in bitcoin, you can invest in Bitcoin using different income strategy, as long as it suits you financially, however most persons use discretionary income to invest because that's the spare money they have after spending on other necessities, this not to say that people who use discretionary income to invest with the mindset of reducing risk factor are out of place, but saying you only need descriptionary income to invest for me is out of place because there are individuals who intentionally want to spend huge amount of the money they have in investing on bitcoin not minding the risk factor others might shiver about, this is because Bitcoin has over the years proven itself that it's worthy of such trust.
I disagree with you dude, because no matter how much someone wants to invest in Bitcoin, that funds must come from the person's discretionary. Remember that an Investor always allocate funds to different needs and wants and these funds should be used for a specific task and so using money outside your discretionary is not advisable and it is a wrong investment and JJG has explained this before now. Even when we want to be aggressive, it is our discretionary funds we will use to...
I believe that these two sides here are pointing at the same truth in two different directions. The thing is that good Bitcoin investment is reduced to risk management, and this is why discretionary income is frequently suggested to people, as it means that you will not be forced to sell all your assets to panic in case the costs of life will appear. Meanwhile, there are more highly-convinced investors or better-financially-shielded investors who make far more aggressive allocations, and history tells us this has been successful in the case of some of them. In my own case, I would consider DCA with discretionary funds as the most secure long-term course of action, whereas I would consider dips as an opportunity to be a little more aggressive provided that your financial capabilities permit it. In that manner you would develop progressively without putting aside money that you could require the next day.