My web site previously offered several categories of an indoor type of product, which have since been permanently discontinued. We do still offer a full line of the outdoor type of these products. The usage is quite different (indoor vs. outdoor), and customers looking for the indoor variety are not likely to be immediately interested in the outdoor ones. But the pages for the discontinued categories and products have built up significant page authority and rank quite well even for more generic searches which are not indoor or outdoor specific. I am interested in opinions on what approach to take for the discontinued category pages and product pages.
Currently, the discontinued pages are accessible by direct link, but have been removed from the site's navigation menus and on-site search. The pages include some messaging for visitors to inform that we no longer offer this type of product, with some links to active categories.
We can remove these pages and serve a 404 error page. Or, we can redirect these pages to the outdoor product category (but all would have to be redirected to a single category, as the specific outdoor categories and products don't map logically to specific indoor ones). Or, we can keep as-is.
I am interested in opinions on approach, either between these options above, or other alternatives.