Any development time listed by a manufacturer is a guide or suggested time so why not carry out your own test using a variety of time, dilution and temperature. Clearly, film manufacturers give reliable information but since I started carrying out my own tests using their information as a starting point I think that I have even more control over the end result. I quickly learned how to adjust development to suit any lighting situation I experience. Testing as I suggest does not take up much of your time and it does increase your confidence when dealing with difficult situations.