It takes about 2 weeks on average, but it can be shorter or longer. usually the worst is over after a few days.
Bathing is unfortunately currently touted around as the non-plus-ultra in bonding.

Unless you are trying to re-introduce near fallen-out boars after a temporary separation (which is not the case with you), it is actually counterproductive. The less you interfere, the better for the boys - as hard as it is for you!
Please take heart from the fact that - unlike you - your boys have natural access to the guinea pig bonding manual and are understanding what is going on on an instinctive level. They experience the bonding process very differently from you.