Re: how long does it take aikido to work
If by work you mean execution time, any technique that won't be eventually executed within 1 second and an half, is going to fail. 1 second an an half is the maximum amount of time you may have in a real situation to place your whole techinique. 2 seconds is far too much.
If by "work" you mean how long it will take to make it work in a real fight, probably forever unless you train with a strong emphasis on martiality (= do not simulate only the techniques, having to apply them within a frantic and not complacent attack ought to be your daily bread and daily simulation. Yet most dojos are not oriented in that direction because they have to maximize participants, and maximizing participants goes against implementing martiality...). In that case it may work in a matter of a few months.
If you mean, instead, how long it will take to acquire its "spiritual" side, it will take just as long as the spirit takes in anything else: a whole lifetime may not be enough and you may need a few thousands more lives, or it may happen in an istant (so I have read).