Simpleads campaigns CPU usage skyrockets after lots of ad impressions

This happens regardless of whether you're counting campaigns by ad impressions or not. The issue is in the function _simpleads_campaigns_complete. On my site, I've got half a million ad impressions, and the table was being counted every time an ad loaded, which was causing the ad to take 6+ seconds to show up on the screen, not to mention pegging the CPU. For people who are running ads by date and not impression, this count is unnecessary, so I moved the counts into an if{} block, which fixed the issue for me specifically. That being said, this will continue to be an issue for sites counting campaigns by impressions and clicks, so for a real fix, I'd recommend creating a summary table that stores impression counts and updating it from cron.