I have never been too critical on my temperture controls as I have processed my 35mm in a paterson tank two rolls at a time. Tried to keep the ambient room temp within 5 degrees of the developer temp. I would store the chemistry such that I would 500ml (1 grolsch bottle) at a time and process 6 films from it. Once 6 films processed discard and start on the next bottle. From memory there is a time compensation in the instructions for subsequent films being processed, but I might be wrong.
Trust this is of some use to you.