Unit obsoleteness: which units I have to prebuild in advance?

[sylvanllewelyn]

In standard BTS games, people usually upgrade HA/WE for Cuirs, or pre-build trebs and upgrade them to cannons. Or pre-build some UUs who keep their promotions after upgrading.

The most standard response so far. I am not a fan of upgrading just to keep combat-related promotions. It's just too expensive.

When would I do it?
- Naval units with sentry or medic. Those are rare, valuable, and upgrading them increases movement.
- Trebuchets into cannons. Both the accuracy kind and the CR3 kind.
- Sitting bull archery units for medic promotions. Attach a great general and it gets medic 3 plus charismatic. Sometimes you don't have horses.
- Aztec jaguar warriors for woodsman 3 plus medic 3.

If you don't have the strategic resources for the unit, then you have to pre-build the earlier version. You have to trade for the resource and then upgrade your units.