Downtime
Downtime is time spent by PCs not adventuring. They may be traveling on a ship, building a homebase, researching, crafting, or otherwise honing their skills.
The GM decides how long downtime will be as determined by the pacing of the campaign.
Some activities, like Learning a New Domain, can only be done over a period of downtime.
For more episodic games, several months of downtime provides ample spacing for the PCs to have their own lives separate from adventuring. For campaigns with more urgency, downtime might only be a day or a week.