Wow, thank you! That's a great idea. Worry about shelf life vs. the mysterious "steep time" has been nagging me as one of the main arguments against getting into DIY liquid.
The "mysterious steep time" still has some merit. The way I interpret it has more to do with giving the individual flavors time to combine - kinda like a homemade soup or sauce that needs to let the flavors "meld". I recently made a blueberry and cream/custard flavor. Right off the bat, it was heavy blueberry. A few days later that has smoothed out, and the vanilla/custard/cream has become a little more pronounced.
I keep it really simple. I have a jug of 50/50 and a buzzload of flavors. I drop my concoction into a bottle and top with the 50/50. I'm not worried about ending with a 50/50 blend, so I don't measure exact PG/VG. That, and my S.O. vapes w/o nic. I can make flavors for both of us, but I have nic if I want.
I'd noticed that my purchased juices would start relatively clear and then darken as the nic aged. That, and I felt the flavor muted over time (although, the fact that I'd let juice sit that long

I find DIY extremely easy. The hardest part for me is to look at all the base flavors and try to figure out what would taste good together