I don't think the suitable time for their listing will come. There is no suitable time here, but it is how the project strategize on how to get their traders or clients interested. If you have good and usable product, people will continue to patronize your services, but if it is all promises, I don't think it will go far.
If cryptocurrency maket will raise like it was in 2017 it will be a sutable time for all tokens but I do not thing that such big growth like it was in 2017 will repeat.