Not sure if this is what you're on about but when I came back from a 4-year hiatus (the previous phase having been largely spent on RFC and DoC) I invariably wrecked my econ when waging major wars. I would get anxious and build way too many troops, drafting without theaters and whipping way too hard. I would also basically ignore all other aspects of the game while prepping for/being at war. Knowing how many units is enough and when to switch back to development mode takes practice, it's something you need to get a feel for. In general in civ 4 you need to be very goal-oriented with everything and have your empire work in tandem towards a particular goal, switching between different phases characterized by different objectives. Building all of the buildings runs directly counter to this.
is not much post-factory era anyway. Say you capture an academy or can save a lot of maintenance by moving. I moved the capital in this game https://forums.civfanatics.com/threads/montezuma-immortal-ntt.692954/.
