Short answer? Sell your prospects what they want to buy. If you have a pizza place and people keep coming in asking for salads, add salads to the menu. If your inbound marketing prospects keep asking about ABM, then it’s time to consider it.
Now there are other factors that go into deciding to add or remove services from your services catalog. Like do the desired services violate any principles or morals that you find important? As an example, if you were dead set against doing anything that was not 100% inbound then ABM might not be something you’re comfortable with.