The best time to buy is when bitcoin price is at its deepest. But knowing its hard to predict whether the price is at its deepest or not, then definitely I would always recommend that the best time to buy is when you are ready to buy and lose some funds. Investing is not all about profits but certainly losses as well, so whether the market becomes bullish or bearish, or when bitcoin halving is around the corner, I guess the best time to buy is when you and your funds and emotions are all ready.
I agree with you that the best time to invest in bitcoin is when we are ready, but not buying bitcoin during the off season and buying during the bull season would be a bad decision. The market has only two trends: up and down, so even if you have money and are willing to invest in bitcoin, but if it is a bullish market, you should not rush to buy at that time because the risk of losing money will be higher when you buy them in a bear market. So when you are ready to buy bitcoin, but you also need to consider the market situation to make a decision.