Every game I play, I seem to develop an army that contains a surprising large percentage of obsolete troops. When I look at the cost of upgrading them, I start to question under what circumstances that makes sense. I'm tending toward the following "rules", but want some input from you guys on this: 1) If the unit has more promotions than new production, it is worth upgrading. 2) If the unit has the same number or fewer promotions than new production, it can be replaced unless by upgrading you create a unit you can't build (like a MG with CG promotions). 3) If the unit is a critical defender for a city facing imminent attack, it is worth upgrading. Under most circumstances, it seems like I can just replace and eventually disband obsolete troops, since the gold cost of upgrading them is far more than the hammer cost of building a new one. Am I missing something?