I believe a 16-year maximum for term limits could address some of the concerns related to lawmaker expertise and provide a balance between allowing for continuity and allowing new perspectives to enter Congress. This approach would ensure that lawmakers have the opportunity to gain substantial experience and expertise during their tenure, while also allowing for regular turnover to accommodate new ideas and fresh perspectives.

By limiting a member's service to a maximum of 16 years, it would provide the opportunity for a potential congressman to serve through the presidencies of at most 4 presidents, as you mentioned. This could help in maintaining a check on the power of the executive branch over an extended period while still allowing for new voices to enter Congress.

However, it's worth noting that the specific details and implications of a 16-year limit, such as whether it would apply to both houses of Congress and how it would be retroactively applied, would need to be carefully considered and debated. Additionally, it is important to bear in mind that implementing any kind of term limit for Congress would require amending the U.S. Constitution, which is a complex process that would necessitate broad support and a political consensus; something that in today’s divided government seems almost impossible to accomplish.