Reefing is a very dynamic hobby, it's never done. If it's not the lights, the algae, the flow, and every other thing that you didn't expect, it's always going to be something. When the reef is happy and the corals are growing well it's just a matter of time before it's something else. Even if the reef is problem free you'll see new corals you want, a new piece of equipment etc.
When reefing becomes a chore or problematic such that you're not enjoying the hobby anymore then it's time to find a new hobby.