It is important before investing to prepare an emergency fund first, so that when there is an urgent need not to sell bitcoin in the middle of the road, anyone who provides emergency funds will be safe from any needs.
This emergency fund is exaggerated at times, it is not the money to pay your usual bills but for unforeseen situations, "which may never happen," so why not try to multiply it with Bitcoin in bull season? Needless to say, your funds in Bitcoin are accessible at any time if at all you have a reason to withdraw it or some of it. Why not take the risk instead of keeping it in the bank and letting the bank make money on you while you earn nothing? This can only be dangerous if you don't have access to your BTC. And who knows, you may never have a need for the emergency fund for years, which makes it wise.
Even if the emergencies may never happen
Yes, it is better to be prepared for so it doesn't take you unawares. precision matters in bitcoin investment.
Are you proclaiming that you invest your emergency fund in bull season to increase it, then sell it back after bull season and replace the funds? That's your trading mindset on display bro and you are craving on short-term gains, soon you would be also selling part of your investments too. Trading of any sort shouldn't be entertained in your accumulation journey so you don't have to make mistakes on the way. You should be very intentional about your consistent, persistent and aggressive purchases only and not having to involve trading practices of any sort into it for your sanity sake.
Having access to your BTC is aimed at self custody and not occasional trading practices on your accumulation journey, lets call a spade a spade and it is good most part your backup funds, if not all, especially emergency funds remain in Fiat, or at most stable coins for easier liquidation in the purpose of the needs arises. Desist from tampering with your bitcoin portfolio as much as you can in order to have an effective investment routine.