In general I think of mobility as a separate issue. If your mobility is pretty close, it shouldn't take very long to adapt. Few weeks like Glenn said above.
If you're really tight or inflexible, it's probably not going to be easily fixed just by switching grips and you will need to do much more dedicated mobility work on T-spine, forearms, triceps, shoulder complex, and chest (which is tight in most people that are not olympic lifters...because they like to train the chest).
In general if you have the flexibility in the first place you shouldn't need to adjust the weight at all.