It seems to be a pattern that when I run Facebook ads I get sales very quickly but after just 2 - 3 days no more sales happens. The frequency the ad is shown goes from 1.5 to about 2.5 after a while. This happens on target groups that are in the size of 50,000 and even 500,000. I'm looking to create consistent sales from Facebook ads.
I agree with the other professional who said Facebook likes fresh content. We do paid advertising on Facebook for the purposes of general branding. It's never been a hard converter for us. It's really hard to reach a specific audience.
Also, with regard to our Facebook page, we always focus on quality content that will provide value to our target audience. Then when we want to advertise, we often will boost a post. For instance, we are hosting an event, so we have scheduled specific posts in the weeks leading up to the event. About a week out, we will pay to boost one of those posts once or twice.