I had a job scheduled to patch starting tommorrow this involved patching osb from a refrigerator leak and new 2 1/4 select red oak. They moved a wall and moved the frigde across kind of a hallway entrance into the kitchen. Well I got a call today stating that the fridge had leaked again. My question is how long should I let that dry out before I go check the damage and estimate the patch again since it will now be a bigger job. The OSB swells rather quickly doesn't it or should I wait a month or so??

OSB is cheap.
Tear it out.

I was planning on tearing it out just wondering how long i should wait to do it. I suggested to the customer too wait a week or so. My concern is that the OSB might take longer than that to show signs of damage (swelling) and then realize i should have torn out further and replaced more.

I would tear it out back as far as the water damage is then install the new osb-and as long as your wood is acclimated to the site then go right over that. Why wait for it to dry? if you're tearing it out anyway? Exposure to air will help the places that don't need replacing dry better too. A day or two exposed with fans running should take care of any moisture that hasn't sat for long to dry.

My fear is that some OSB that didn't appear to be damaged could have still got enough moisture that it would take awhile for the damage to show up. My first thought was to go ahead and tear it up but then I started thinking (always gets me into trouble) that maybe some OSB would appear to be fine but it actually would be wet enough to cause damage just not instantly. Thanks for the replies

That's what moisture meters are for. Why guess? Check the subfloors with your meter. That will tell the true story.