The reason I use Series collections is that the plugin can automatically set the sort order. Unfortunately I end up with far more than double the amount of collections I would have if I used author collections instead. One author often has 3 or more series, where seldom does a series have more than one author. This is probably the main reason my collections take over a minute to open.
I prefer author collections but I am used to readers that have a global sort for all collections and I forget that this is not so with Kobo. Not saying which is better, but habits are hard to break and I often select the wrong book on the kobo if I use author collections. Small thing but annoying.
If I have both author and series collections than the delay is worse of course.
A big downside of having only series collections is that non series books do not show upon the collections menu. I assign a no series series with a custom column so I can access them from the collections menu but this again adds time.
I would love an option to have all collections sorted by author as this would cut down my time problems opening collections quite a bit. Doesn't need to use date added as I use a plugboard. Probably I am wishing for the moon
Helen