The "default age view" is set individually by forum. OS was set to "last day", GS was set to one month. I went ahead and re-set OS to one month as well, since overall, they have about the same number of threads, even though OS is getting more posts. Now I see 19 vs. 20 pages for that time period, so they're about on par.
But as lomn75 mentioned, you can change the setting on each forum page and go back further into history.