2 of my 4 previous tanks lasted about 10-12 months. My current system is about 2.5-3 months old, and I entered the ugly stage pretty early. I’d say around week 4 is when I got the heavy green on my rock. About 2 weeks after that, the heavy green turned a bit slimy, but at the same time I started having coralline patches pop up (super early for a tank. I was blown away). A week ago, I got back from vacation to an algae ridden tank. My coralline colonies are still growing and have developed quite a bit more, but the algae is pretty dominant. Who knows how long it will take. It seems every tank is different.
Here’s where my tank is as of this afternoon.