The final regulation regarding recalculation of the applicable distribution period is 1.401(a)(9)-9(f)(2)(ii):
(ii) Determination of applicable distribution period —(A) Distribution period based on new life expectancy . With respect to a life expectancy described in paragraph (f)(2)(i) of this section, the distribution period that applies for a distribution calendar year beginning on or after January 1, 2022, is determined by using the Single Life Table in paragraph (b) of this section to determine the initial life expectancy for the age of the relevant individual in the relevant calendar year and then reducing the resulting distribution period by 1 for each subsequent year. However, see section 401(a)(9)(H)(ii) and (iii) for rules limiting the availability of a life expectancy distribution period.
While IRS Pub 590-B says that you "can" recalculate the distribution period, the final regulation seems to say that you must recalculate. For most (but not all), that means a lower RMD.
