The Warblade class feature "Weapon Aptitude" permits transfering weapon specific feats to another weapon. The description reads:
You also have the flexibility to adjust your weapon training. Each morning, you can spend 1 hour in weapon practice to change the designated weapon for any feat you have that applies only to a single weapon (such as Weapon Focus). Tome of Battle, p.22
That this training can only be done in the morning seems to follow the "fresh mind" concept of learning spells for the day. But how long does the change last? Is it gone next morning or does it last until there is a new training session? In the case it has to be refreshed each day: Does it last after going to sleep, in case of a night time ambush?