Indeed, here is my logrotate configuration for apache:
create 640 root adm
/etc/init.d/apache2 reload > /dev/null
if [ -d /etc/logrotate.d/httpd-prerotate ]; then \
run-parts /etc/logrotate.d/httpd-prerotate; \
Notice that it is done weekly and it issues a reload postrotation. I think the mystery is solved.
For me, this actually has a nice side benefit that my APC cache will automatically be flushed once a week. The thing that had triggered me to look into this in the first place was that I was inspecting my APC cache statistics and noticed that it was using less memory than I expected. I was concerned that it had filled up, but saw that cache full was zero. Then I noticed that it had been running for just over an hour. So, I checked my log files and noticed the Graceful restart. And, now here we are at the resolution. Cheers!