When you go to all the effort to make a condiment from scratch, you want it to have some legs. It should last at least a few weeks; even better a couple of months. Let me introduce you to the art of culturing.
The vegan mayo was a happy accident. I was trying to make a different version of home-made margarine last year, tried agar agar instead of lecithin, and ended up with creamy, fluffy, cholesterol-free and salmonella-free mayo.