if I search all my posts or threads via the functionality on my profile, the results only show a fraction (last year or so) of content
if I instead use the advanced search, with me as author and a range of dates (from 2011 to now; since I cannot go further back than 2011 there either), it will always only show up to 5 pages, even if this will not include the whole date range
You can search for topics or posts made under “advanced search” (the gear next to the search box) by typing your user name and select either “Search title and content” or one of the other options.
It seems the result is only limited to 5 (?) pages. You can actually show older posts by changing sort order to “ascending”. If you didn’t limit the pagination, I think the OP would be happy. If this is a drupal view (?), I know it’s easy to fix.