The time between a website being suggested and it being reviewed is an unknown period of time.
Unknown, unknowable, and completely irrelevant.
(Which, unfortunately, doesn't keep people from asking it over and over.)
Here's the thing. There's only one time interval that could ever, conceivably, matter. And that's the time from when a website, with listable content, is online and functional -- until the time it's listed.
What does the suggestion date matter? Not at all. An unsuggested site is just as worthy of consideration as a suggested site. (And an unpromoted site is actually more likely to be listable than a promoted site.)
What then is the point of a suggestion? Just this: to try to reduce the time period that matters. Unfortunately, since, in reality, so many suggestions actually INCREASE the time that matters--that is, they divert editors to unlistable sites--they often get the respect they deserve (which is a great deal less attention than site owners want.)
So it comes back to this. The five minutes to review, describe, and categorize a site. The editor wonders how many worthless sites--from search results, suggestions, whatever--have to be gotten past to find the gem (and never knows). The site owner wonders how many other sites editors will review before thinking is site is the best possible candidate left for review (and never knows).
All anyone can know is, a well-written suggestion, made to the appropriate category, will make a site more visible to the person most likely to be interested in reviewing it. (And "who would that be?" is another one of those "nobody knows and nobody can ever know" type questions.)