So How Long?
In Oklahoma, the answer is two (2) years. Everybody has heard of the statute of limitations for crimes (thanks, television!), but not everybody knows that there is usually a limit on how long a plaintiff can wait prior to filing their lawsuit. That limitation is found in 76 O.S. §5.5.
Isn't this Really Short?
Yes, I think it's really short especially given some of the complications that can exist (like a guy in a coma, for example).
What Happens if I Wait Longer?
You lose the ability to collect on your claim because you give the defendant (and his insurance company) a bar to recovery that they can assert which will be upheld by the courts.
Why Would This Be?
Well, "it's the law and the legislature writes the laws" is the direct reason. The legislators receive advice on what the law should be from various people who have conflicting ideas about how the law should work and from among those ideas they choose and vote and, if the governor approves, then the idea the legislature picks becomes the law. Reasonable people can draw inferences about whose idea won the contest in this case, but there is also reasonable logical reason about why there would be a limit on how long a claim can be made.
The logical idea is that it's really difficult to defend a claim that is really old. For example, if you could sue someone for something that happened 100 years ago that wouldn't really be fair to whoever is being sued because any evidence about the claim would usually be extremely limited because things and memories deteriorate over time.
However, two years is, in my opinion, unreasonably short given technology and other changes that have occurred in the last hundred years. A more reasonable amount of time would be three years like the criminal statutes or even five years like the limitation on a written contract.
I don't write the laws, but I can help you deal with them. The upshot of all this is that waiting to assert your claim is a bad idea and can cause you permanent financial damage in the long run if you're the victim of a bad or careless driver. If you have a claim you need to talk to a lawyer as soon as possible.
If you're the victim call a personal injury lawyer at (405) 310-9890. If you caused the wreck call your insurance company.