I am pretty sure that fiat currency will never completely disappear or even if it is no longer used there will definitely be an upgraded version of it that will be introduced and will still be created by the government. So waiting for fiat money to disappear is just a waste of time and meaningless.
I invest in bitcoin and want to become financially free and have a better life. I don't think it's my responsibility to hold on to bitcoins and give them to my grandchildren while my parents, wife and children have to live a difficult life. There will be no freedom if you still live in poverty and don't have enough money to take care of yourself and your loved ones right now.
I also think regular money will still be around for long time and even if it is replaced government will create new version. So waiting for regular money to disappear is waste of time. I also invest in bitcoin to have better life and be financially free. My family needs are more important to me than holding onto bitcoin for future. I want to make sure my loved ones are financially secure and comfortable now. True freedom means being able to support myself and my family today not just saving for future. And if you ask me I also believe in finding balance between investing in cryptocurrency and taking care of my family financial needs today. As you know both are compulsory.