Hello and welcome,
Like others have said, Niantic has never disclosed how long it takes for nominations to be resolved; all info provided is based on what other Wayfarers have noted for themselves. It really depends on how many reviewers are in your area, as well as how well their review ratings are, to get to resolution. Here’s the info from the Wayfarer FAQ:
How many reviews does it take to make a final decision on a Wayspot’s eligibility?
This exact number cannot be disclosed at this time, however, we can say that this depends on the performance of each individual Wayfinder.
Here’s what an upgrade actually does: it opens your nomination up to a wider review area. For example, I’m in the US, and in an area with few reviewers, so at times, a non-upgraded nominations can take a few weeks, even months, for resolution. If I upgrade, then it’s open to most reviewers within the US, and I typically see resolution within a few days. Here’s what is included on the Upgrades help page in regards to this:
Note: Upgraded nominations increases probably that your nomination will be reviewed by the community faster, but do not guarantee a specific review period. Upgraded nominations must still adhere to the same criteria as standard nominations to be accepted.
Again, it depends on your review area, the number of reviewers, as well as how many nominatinos are in queue. That last part is something you can help with, as when you review, this helps bring the queues in your area down, and will help your nominations get seen by other reviewers.
Lastly, since ML was put in place, it has been taking anywhere from 24-48 hours to make a decision on a nomination. If after 48 hours you haven’t received a ML resolution (emails will say “our team”), you may want to consider an upgrade, but it all depends on how fast a non-upgraded nomination gets resolved for you. More urban areas tend to have faster resolutions, as they may have more reviewers, whereas rural areas may take longer.