Answer: I will hedge a bit and use an attorney-like response on this question. The answer to this question is "it really depends." Some factors involved consists of: the facts of each case, what time of year it is, who the defendant car manufacturer is, who opposing counsel is, client expectations, and sometimes luck.
Each case, although similar on some level, is different. Cases that are filed near the holidays (for example, Thanksgiving or Christmas season) understandably takes longer, as employees of involved parties are more difficult to contact, interview, and obtain evidence.
Some vehicle manufacturers drag their feet and purposely take forever to respond to a claim -- they have very little to lose by taking their time, their goal is to take advantange of an impatient and frustrated consumer. After a demand letter has been sent and a law suit is filed, the claim gets forwarded to an opposing attorney for the vehicle manufacturer and car dealership. Some attorneys are professional, while others like to play bulldog.
Sometimes, clients are patient, while others are uneasy and are ready to move on with their life. Clients have to ask themself what the value of stress in litigation is worth to them.
Believe it or not, luck plays an important role in litigation. Often times, I handle two lemon law cases that are very similar in fact pattern; one gets a repurchase settlement while the other takes up to 4 to 5 months and gets close to trial.
Having discussed these variables, the average timeframe is anywhere from 1 month to 5 months. Cases that go to trial may take longer.