I'm just starting to make my own and am curious if steeping is needed if there no nicotine.
Steeping e-juice is not possible, since you are not extracting flavors from a solid (such as tea leaves). However, curing your juice is beneficial even for 0 nic, as gentle heat and exposure to the atmosphere will allow for the release of perfumey volatiles which aren't that pleasant to vape.
If it tastes bad from the beginning, it will most likely never taste good. IMO there is a bit of a myth in terms of "steeping" beyond 24 hours. Tobacco flavors and things like that may actually benefit from a longer period of time, but IMO 24-48 hours most fruity flavors, etc. have reached their prime until it is just the old juice taste you are after.
Both "steeping" and "curing" seem like the completely wrong terms as I see no reason "curing" is any more accurate. Age makes more sense. Oxidize? maybe, we need a chemist to tell us what is actually happening.
A buddy of mine makes really excellent juices. He will mix them up, we try them immediately, and they are delicious. They can change after about 24 hours, but in general I would say you can tell if it is going to be good or not immediately.
This is not the gospel of course but I do think there is a certain level of hive-mind ignorance within the vaping community, or the internet in general. Something to consider.