Generally, an at fault driver is responsible for your rental fees for a "reasonable" time--the time it would take the average person to get a new car. (It does not matter if for some reason it is taking *you* longer: the law deals in what usually or reasonably occurs.) Two weeks might be about as long as it would normally take; if you were to sue--and the only way to get more money if they don't voluntarily pay is to sue--you might not be able to get much more than the 2 weeks you've already gotten.