How many days have an attorney necessarily devoted to preparing for a trial?

The court is of the opinion, as set forth in the case of Walton v. Howard, supra, that no rigid rule or formula can be devised by which it can be determined how many days were necessarily occupied in preparation for a contest or trial. However, it is also of the opinion that any days which are claimed by an attorney to have been necessarily occupied in preparation of the contest must be days in which the employment of the attorney was substantially devoted to such preparation.