Hides and living space
Easier said than done. I have 20 gallon tanks for both of my leos and there's barely enough room for three hides in there if you are also including other things like water dishes, food dishes, calcium dishes, and something for them to climb on.
My first leo Bahamut would probably get bored stiff if I replaced his climbing log with another hide as he seems to love climbing on warm nights. As of right now I have a hollow log hide in there for him and he seems to have found another hiding place under the right end of the log. I don't see how I could put any more without drastically restricting his living space.
Then again, if you have something considerably larger, I would say go ahead. I don't see that happening to me though. Whenever I get something bigger than a 20-25 gallon tank I end up wanting to use it for something else.