I have long wondered how even when I have conquered a third of the map using the same few stacks to do the job I will come across a stack owned by the AI which has units with 3 silver chevrons of experience despite their empire being small. I have fought countless battles and the AI units I swear have done hardly anything yet my infantry and missile units will be lucky to have three bronze chevrons. Cavalry seem to pick up experience pretty easily, but in my experiences infantry is a different matter.
Are there any people out there who can give me good advice on certain tactics or anything that will allow me to have elite units after a century of waging war with them?