Length of time from action to accusation has absolutely zero to do with credibility. No matter how much you want that to be the case.
Time does matter. The reason why is that our memories are not terribly good for the most part. When time elapses, facts, biases, illusions, often creep into our accounts of stories. And, real facts become much harder to prove as a result.
This is one of the main reasons why mostly all crimes and matters of civil liability have statutes of limitation. Because the further time moves away from an event, it is usually much, much harder to substantiate. This is especially true in matters between individuals without any physical documentation
For example, if you messed up your tax return X years ago and did not pay enough, we can always go back and look at the numbers and calculate. But, if you alleged that I punched you in the face with no one around, no pictures, etc. and then a year and a half passed until you went to the police, your story becomes very hard to prove.
Severe sexual assault (meaning, things like Blasey Ford alleges as opposed to the Frieden story) in general can cause a lot of mental fraying resulting in people taking a long time to even be able to recount the story without breaking down. We have scientific evidence on this matter. Unfortunately, with that time elapsed, things often become infinitely more hard to prove.
There has been a lot of discussion about Blasey Ford in this thread. She, as a person, did not seemingly lack any credibility. And, some of the treatment towards her personally when she testified by those asking her questions was incredibly poor.
However, an event 36 years in the past, with the first documentation of the event 30 years after it happened and a lot of people that stood on contradictory sides of what happened in itself is not a terribly credible story.
I am not denying her recounting of the facts, but just on a strictly evidence basis, she did not have much that would be substantive. A court case of no kind could ever be amounted against Kavanaugh with the facts in question and the time elapsed.
A Supreme Court Justice is a lifetime appointment to one of the most important positions in this country (and the world). It opens a person's entire life up to scrutiny. As a result, I think it was right for Blasey Ford to be heard. And, the fact that other accusers of similarly situated behavior by Kavanaugh stepped forward showed that he likely had a pattern of poor behavior around 35 years ago even if her memory was clouded by time (and others who made similar accusations in that period).
Then, the question turns to whether this is a person that should sit in such a prestigious, lifetime position. And, it is not an easy question morally though I think both sides of the argument are clear.
Stepping forward with an accusation of anything does not make the accusation credible. The facts surround the accusation make it credible. And, we certainly give some weight to the credibility of the person.
But, to the main point of my post, time means a lot. And, something with all of these situations where people either were or feel wronged is that when more time elapses, the story begins to become much less credible. Blasey Ford's accusations happened in a time when people were mostly conditioned to not come forward for such situations. Bolton's occurred when people have been conditioned to come forward.
It goes back to something that we talked about when Pat Narduzzi was under the scope, which is that we really need to teach kids from a very young age to assert themselves situation and report things when needed. It would/does prevent a lot of future issues though we see with this Bolton example that someone could do the right thing and still be brushed aside.