An advertising campaign is not something you switch on and leave. It always goes through three phases, and knowing which one yours is in is what tells you whether to leave it alone, adjust it or switch it off.

Phase 1: the start. You launch the ad with its audience and its budget. For the first few days Meta is learning who to show it to, so the numbers jump around and do not mean much yet. What helps in this phase is having launched several versions of the ad at once, so that the system can find which one pulls best.

Phase 2: stability. After the first forty-eight hours the numbers settle and can be read. Here the work is watching and making small adjustments: raising the budget of what is doing well a little, trimming what is not. What you look at every day is what getting a customer costs you and how much each euro spent gives back (see «Which numbers to watch and which to ignore»).

Phase 3: decline. It always comes. People have seen your ad too many times, they stop reacting, and what each customer costs you starts rising. The signals are three at once: frequency rises, which is the average number of times each person has seen your ad, the share of clicks falls and the cost per customer rises.

When that happens, pausing is not enough: it has to be replaced. If you only switch it off, you stop selling; if you swap the ad for a new one, the campaign starts up again (see «When an ad has burnt out and what to do»).

Who does this in Markettai. BOOST, the automatic system, watches these signals all day. If an ad's price runs away and it is also clear that you have worn out the audience, it pauses the ad without asking, on any paid plan. Every other change is either proposed to you or carried out on its own, depending on your plan and your settings (see «What each plan automates»).