(1)General. Any B-1 visitor for business or B-2 visitor for pleasure may be admitted for not more than one year and may be granted extensions of temporary stay in increments of not more than six months each, except that alien members of a religious denomination coming temporarily and solely to do missionary work in behalf of a religious denomination may be granted extensions of not more than one year each, provided that such work does not involve the selling of articles or the solicitation or acceptance of donations. Those B-1 and B-2 visitors admitted pursuant to the waiver provided at § 212.1(e) of this chapter may be admitted to and stay on Guam for period not to exceed fifteen days and are not eligible for extensions of stay.
(2)Minimum six month admissions. Any B-2 visitor who is found otherwise admissible and is issued a Form I-94 (see § 1.4), will be admitted for a minimum period of six months, regardless of whether less time is requested, provided, that any required passport is valid as specified in section 212(a)(26) of the Act. Exceptions to the minimum six month admission may be made only in individual cases upon the specific approval of the district director for good cause.
a. (U) Although 「temporary」 is not specifically defined by either statute or regulation, it generally signifies a limited period of stay. The fact that the period of stay in a given case may exceed six months or a year is not in itself controlling, provided that you are satisfied that the intended stay actually has a time limitation and is not indefinite in nature.
b. (U) The period of time projected for the visit must be consistent with the stated purpose of the trip. The applicant must establish with reasonable certainty that departure from the United States will take place upon completion of the temporary visit.
c. (U) The applicant must have specific and realistic plans for the entire period of the contemplated visit.
d. (U) In evaluating these cases, you should not focus on the absolute length of the stay, but on whether the stay has some finite limit. For example, the temporariness requirement would be met in a case where the cohabitating partner will accompany, and depart with, the “principal” alien on a two-year work assignment or a four-year degree program.
Up to 6 months; maximum total amount of time permitted in B-1 status on any one trip is generally 1 year.
这个表格说：B-1 签证入境时给的首次停留期限最多 6 个月，延期最多 6 个月。单次停留（on any one trip），「通常」（generally）不超过 1 年。也就是说，包括延期在内，单次停留最多 1 年。当然他也说了是 「generally」，不排除有例外情形。但是，就在这个表格的下面，又说：
At the port of entry, an immigration official must authorize your admission to the United States, and, if you are eligible for admission, you may be admitted initially for the period necessary to carry out your business activities, up to a maximum period of 1 year. If you who wish to stay beyond the time indicated on the Form I-94 without departing from the United States, you must file Form I-539, Application to Extend/Change Nonimmigrant Status, and submit any required supporting documents to USCIS. For more information, see the Extend my Stay page.