A lack of updates

Both the excitement and the frustration of aquarium-keeping tend to come within the first few months of setting up a tank. Algae outbreaks tend to be par for the course. New fish bring with them a fascinating repertoire of behaviours, but can also bring problems (disease, conflict, failure to thrive). And the plants you put so much effort into setting up and arranging just the way you want them seem to have a mind of their own. Some you hoped to fill out die or get uprooted, while other spread like weeds.

After a few months, things tend to work themselves out. The fish adapt to your tank and to their new tank-mates. The plants get established (or die) and your main concern tends to be trimming them back and working on a coherent aquascape. (There's always the challenge of filling that one troublesome spot, or that one troublesome plant, but it tends to become a minor annoyance you're happy to live with.) Algae problems never go away, but they fade into the background. All is well and you can sit back and enjoy your tank.

That's about the time you start thinking about setting up a new tank, and replaying those problems all over again.