I've been planning my 29g setup for about 2 months now. I have my stocking list possibilities written down as well as ideas for what plants, different substrates, driftwood etc. I want to get it right the first time that way when its fully established I won't have to mess with anything.
I'm the same way. I even have the piece of driftwood that I wan planned out. I've been planning it now for around 6 months. The only thing holding me back right now is money. The tank is already cycled with some live plants, but I had to stop because the funds ran out.
Space is another obstacle that is preventing me from expanding. I have a tank on each wall of my bedroom, and the rest of my house is full of other stuff. Right now I'm trying to move my bettas out of my room to give them some more interaction.