When is the best time to purchase an amtrak ticket?

Question

ie. how far in advance

Answer 1

Im going from NY-Chicago next month (overnight with sleeper) anyway purchased three months ago.This type  should be purchased ASAP.

Answer 2

Obviously the further ahead the better.  I would say at least 3 months will get you the best rates at the time.  Having said that, if you are flexible they do have those last minute deals, like the airlines. that are fantastic rates.  They use this to fill up the unused seats but usually you have to travel within 2-4 days of when the rates are published.