Blizzard plans to massively shorten the time it takes to reach Artifact Knowledge 40 for returning players.
We’re currently working on a hotfix intended to significantly reduce the amount of time it takes to reach the Artifact Knowledge cap of 40, in order to allow returning players to catch up more quickly.
Specifically, this hotfix will reduce the time it takes to research ranks of Artifact Knowledge between 26 and 40 to approximately 4 hours each. We hope to make this retroactive to any work orders already in progress when the hotfix is applied. Once these changes are live, a returning player should be able to reach the maximum level of Artifact Knowledge in only a few days.
This hotfix will require extensive testing, but our goal is to apply it within the next day or so.
Source: blue post