It's been a while since I've done a deep dive into one of these issues but If you are uploading the data in the Customer Attributes interface I want to say it was 24-48 hours. If you built out a segment in Audience Library the rules would kick in within a few min and I think the Audience name would show up in Target within a few min. If you shared it from Analytics as a historical audience, it would take longer.
I'll see if I can get someone with a bit more recent experience to chime in here as well.
Hi mikewebguy1 or MikeWebGuy-trOkXL - any chance you know the answer to this question? How soon are updated customer attributes are available in Target Standard audiences after uploading files into People Core service?