If the job post sets a specific limit for the sample length, you should always go by that. If the limit is not set, writing samples that have eight to 20 pages are usually the best. They provide enough substance for the employer to evaluate your argumentation, persuasiveness, and analytical writing skills. If the sample is specially packed with analytical reasoning and arguments, it can be a bit shorter than the eight pages; however, more than eight is preferred to provide enough content and legal analysis to evaluate.