Months, typically. But it depends on a lot of factors, like:
Are the links pointing to the GMB landing page URL
How relevant are the sites from which you've got the links
Are they cheapo links anyone can get
Is it just a blast and then you don't get more links for a while, or part of a steady stream and long-term project
Are those your first or only good links so far, or are they the latest in an already-high body count
Are your rankings solid already or just squeaking along
And so on. Expect for it to take a while. The lag time is unavoidable and, I suspect, intentional on Google's part. One can only imagine how much worse the spam situation would be if people could instantly see the benefit of this link or that link.
New advertising option:
A review of your product or service posted by a Sterling Sky employee. This will also be shared on the Sterling Sky & LSF Twitter accounts, our Facebook group, LinkedIn, and both newsletters.