I like playing games on AoE II that last days. For this use case, I can remove the population limit, but I cannot remove the map size limit.

I expect that this is because the map is precomputed rather than generated chunk-by-chunk on-the-fly.
This would finally allow me to play a game for weeks rather than days, something that I’ve always wanted.

Yes, the map sizes are prefixed.

You could play with longer lasting resources so that you have to move less often.

So if you want to run from enemy you give longer lasting time to move?

What, slower units? No. There are maps where you can have thousands more resources. Check my workshop.

I mean if you are about to get attacked like in a radius of 5 blocks if enemy sighted. The enemy units getting movement speed slowed down to dead and need to allow the player to run away and get thousands more resources with in the given space. This will be continued until the enemy kills enough bases like 5 times the enemy kills a base in the same location if you could not make a infinite map size. You need to at least allow the player to run and make more number of bases.

This would finally allow me to play a game for weeks rather than days, something that I’ve always wanted.

You could either play with unlimited resources or create a scenario with a trading component or re-growing resources near your town. Then you could play for weeks. You could even play with 1k population enabled, imagine all the farms you could have that way...

Regardless, I think the issue is more that the game was not designed for such long games. Civilization would come to mind as a strategy game with way longer matches.