Best practice for clearing sub-filters?

This question is about a site under development that searches both academic books and conference papers. Users can search All, Books, or Paper Abstracts. If searching All, users can then filter search results by either Books or Paper Abstracts. In each case, sub-filters are displayed. For Books, the sub-filters are related to Book Reviews and Years. For Paper Abstracts, the sub-filters are related to Meeting Type and Years.

This question has to do with the sub-filter... Years. Note that the range of years displayed in the sub-filter for Books is different that the range of years displayed in the sub-filter for Papers. The Years displayed for when filter by Books start with "Up to 1970", but the Years displayed when filtering by Papers start with "2001 to 2005."

Currently, when users first filters by both Books, then select Papers as their primary filter, both sub-filters (Book Reviews and Years) are cleared. By the same token, when users first filter by Papers, and then select Books as their primary filter, both sub-filters (Meeting Type and Years) are cleared.

We have a business owner who is making the argument that, in the scenario above, only one of the sub-filters should be cleared (i.e., Book Reviews or Meeting Type) but the Years sub-filter selections should carry over from one content type (e.g., Books) to the other (e.g., Papers). When I pointed out that each Year sub-filter has different ranges, then he insisted that the Years sub-filters should hold the selection where the ranges overlap.

Can somebody speak to best practice in this scenario? I either need to update the functionality accordingly or notify the business owner that we are following usability conventions by clearing sub-filters when users change selections of the primary filter, even when such sub-filters have overlapping characteristics. (Any links in that regard would be helpful.)

Thanks in advance!