It's conceivably relevant to you, but when weighing the credibility of a claim and/or an accuser, it is irrelevant -- except as a means of assessing that the person who believes it to be relevant is uninformed.
Here's why in general terms: NSVRC estimates that 63% of all sexual assaults are not reported to the police. You likely know the reasons for this, but just in case: fear of not being believed, low prosecution/conviction rates, frequently insurmountable burden of proof given the specific nature of most rapes, the fear of an extended criminal trial, victims blaming themselves or in some cases (including one of Brand's accusers) not wanting to admit that they were raped (easier when many violent sexual assaults are not the cartoon example of a man in a balaclava in the park, but someone you know and had previously trusted).
I presume that you accept that there are, in general, many women who are raped and simply do not come forward, and that the passing of time in such cases does not in any way diminish their claim?
More specifically, in California, the law reflects this uneasy reality for victims: from 2017 onwards, there is no statute of limitations on rape accusations. It's not possible for the criminal standard of proof to be changed to account for the fact that, axiomatically, rapes are difficult to prove, therefore the state grants an unlimited amount of time to come forward, which gives prosecutors the benefit of being able to build the most robust case possible.
Proving criminal actions beyond reasonable doubt literally means that the court/jurors find the evidence so compelling that no reasonable person could conclude anything other than guilt. And in a similar fashion, California's penal code seems designed to say that no reasonable person could find a decade passing between a rape and the victim coming forward as relevant to the credibility of the claims.
It's simply settled at this point: coming forward about a rape is a brutally unfair, hard, and thankless task. That's why the vast majority of victims do not come forward. That's why it's important that we understand what it means to "believe women": it doesn't mean that we abandon legal principles and convict men at the whim of their accusers, it means that we collectively create an environment in which the victims of serious, life-deranging, deeply personal, embarrassing, hard-to-prosecute crimes are not given yet another reason to do nothing by people who don't seem to understand that there are vastly fewer false accusations of rape than there are unreported ones. It needs to work the other way around.