It's many hours now that the paid CPC is lower than my bidded CPC.
I read in another thread that i should be gentle lowering the bid if i don't want to lose traffic. Something like 8 cent every 8 hours (at least) if i remember.
BUT
When it's the right moment to lower my bid ? When i pause the ad or while it's running ?
I tend to change my bid prices while the ads are running... I'm usually watching my tracking too to see how it is affected.
I don't usually touch bid prices until at least a few hundred clicks in. Once I do start lowering it, I try to keep an eye on my traffic to make sure I'm not choking the campaign. Sometimes a difference as little as .10 can stop traffic completely...
Lower when it's running, and definitely be gentle.
Lower when you have atleast 30 clicks on the ad. If you share your CTR and suggested bid i can help you choose an appropriate lowering path.
My recent campaigns have all involved massive CTR take offs, so I'll get 100s of clicks in a few hours. When this happens, say my bid was $0.25, CPC dropped to <$0.05, I just left them running and capped my bid later at e.g. $0.07 (based on EPCs etc). I tend to bid high, let CTR determine the CPCs and then cap just above them later on provided I have a decent number of clicks. I don't think you gain much lowering bids until you've established your highest performing ads and they have stabilised and had at least 30 clicks, as above.
I tend to notice the CTR having the biggest effect on CPC, with the bid reduction mainly reducing CPC spikes (i.e. you pay ~0.25 a click, then one random one costs you 0.37) and capping the maximum, later choking traffic if you drop too far. You really have no idea what FB expects you to bid to maintain traffic so it's really a process of testing. In the past I think I noticed the traffic dropping a bit when I got within about $0.05 of the CPCs I was getting.