Ohhh... that's not an easy question to answer without actually timing it on a scope... it will depend on the number of bytes you're reading at a time, etc etc.

But as a guesstimate, reading back say 8 bytes in one block (sequentially grab Registers 00-07), you might need as many as 150 bits at 100kHz... so I guess it could be as short as 1.5mS, and under 1mS if you're just grabbing the first three Resisters for the TIME only.