Seems kinda silly, doesn’t it? After following all the Apache performance tips found on Google, I noticed that the site I was tuning (rss2.com) had access logs exceeding 2GB in size. Now if you imagine each httpd process having to load a file that size, you can imagine why it took so long for new httpd processes to load.
I configured logrotate to rotate logs each hour when the logs exceeded 100K. What a difference! Of course, restarting Apache every hour helps, too. But the change made a significant difference.