Covenant questline?

I believe there are 9 chapters? how long does this take to finish? say if you’re playing 12+ hours a day?

That is hard to say because the higher chapters are gated behind renown level. To get the quests in chapter 9 you need to have level 22 renown with the covenant. Some of the calling quests reward renown. End quests from the chapters reward renown. The weekly quests to provide anima/rescue souls provide renown. Therefore, depending on how many of these types of quests you do is going to be the real indication of how fast you can complete the chapters. Any specific chapter can probably be completed in an hour, so that should not be a problem…just renown.

As an example, here are the date/times of when I completed each of the final quests in the Venthyr Campaign chapters:

2021-01-04 11:04
2021-01-04 13:20
2021-01-06 19:36
2021-01-08 17:39
2021-01-13 15:27
2021-01-14 18:47
2021-01-15 16:18
2021-01-16 10:27
2021-01-16 15:29

As I said, most of the waiting was just getting renown levels high enough.