Training raw recruits from combat level 10 to level 20 takes approximately 7 months under a General with a leadership level of 100. A trained soldier with combat level 20 takes 9 months to train up to level 30. By the time the raw recruit has reached level 60, approximately 4 years later, the trained recruit has reached a level somewhere between 64 - 66. Unless money is no object, consider training only raw recruits. Downside to this strategy is you must conscript, which lowers the overall loyalty of your village. Taxes will not be levied as quickly using this strategy.
One possible strategy, when expecting a game of military conquest, is to train a soldier to Leadership/Combat skill 20. Promote him to General and build a fort. Conscript 8 raw recruits into his fort. His leadership level will rise to 80 in approximately 2 and 1/2 years with a combat skill of approximately 57. During the same time the recruits will only be at combat level 30 (the downside). As his leadership skill rises, so will the recruits combat level.
Opening links to buildings (except forts) will allow villagers to migrate to jobs. This does not lower the loyalty of the village. Use the conscript option sparingly. Each conscription lowers the level of loyalty in the village resulting in longer waits between automatic taxation.
Add a training strategy here.