Replenishment of the Imperial Army and losses.

[Dagann]

3) Early Empire: Legions receive piecemeal replacements along time. They would never be at full strength, but that is not surpriing, no army is at full strength, not even modern armies, to attain it is very much like Full Employment in an economy.

I agree, but during the 1st and beginning of the 2nd century, a standard legion on the limes would be around 5000 men, even not at full strenght. May be 4000 in the worst situation. I'm not talking about particular situations such as Legion VI Ferrata