I Am at level 151, just finished Chapter 30, why am I still renovating the lighthouse?

Also note, the landmarks only depend on how often you renovate and has no relation to your level or how fast or slow you progress your game.

It takes about 6 months give or take (IF you renovate every day and don’t miss) per landmark.

The lighthouse is the fastest landmark to complete, having 141 steps to fill, which if you renovate 2 steps daily, takes 141 days or 4.7 months. It is faster if you renovate every 20 hours, but that takes true dedication and a set timer. Landmarks are steady supplies of flowers, and are meant to last a long time. Here's a chart of all the landmarks and their completion times:

If you renovate 2 steps every 24 hrs:

Lighthouse (20 levels) 1+4+8*17= 141 days = 4.7 months

Chapel (20 levels) 9*19= 171 days = 5.7 months

Pirate Ship (20 levels) 10*19= 190 days = 6.3 months

Mountain Chateau (20 levels) 12*19= 228 days = 7.6 months

Aviary (6 levels) 12*5= 60 days = 2.0 months

I'm at level 218, and I just recently finished the lighthouse. I renovated every day, but it takes a long time!