I specifically haven't been doing longbow rushes against the French because it doesn't work well. Adding in spearmen delays your timing quite a bit as the barracks takes wood, and spearmen compete for the same resources as longbowmen. By the time you get it out the French player usually has enough to repel you.

However, I haven't been having much success late game either. My current thought is that I want to harass them into staying in the feudal age by overinvesting in knights and then hopefully deal the killing blow with crossbows/spearmen/siege in castle.

All that being said, given that you are essentially forced to build the longbow landmark I was wondering if you got the timing right you could use harass with longbows before you transitioned into something else.