While I have aimed to keep my WIP 2600 homebrew Penult within 64K, I've always known there was a possibility that it could go to 128K. Maps and text strings take up a lot of this space, and I'm going to need a good amount more of both to finish the game. What made me make the choice to switch to 128K was sitting down and doing the math comparing what I have planned with what space I have left. I'm looking at dungeons now, and those maps alone will use up much of my remaining space.
The good news is that I've successfully switched my code over to a bankswitching scheme that supports 128K (DFSC as described in this topic), so I can continue development without worrying about running out of space. I'm curious now if anyone has published a 2600 homebrew game that was this large yet?