Keep the water bath at elevated temp if you must, and pop the chems in a few hours before you need them.
I have good luck using a typical 'cooler' or 'Esky' if your are oz/kiwi to hold my water bath.
My setup has a fish tank pump to move water around, and a fish tank heater, that I have set at 100F and sealed up with 'duct seal' electrical conduit sealing compound. This goo keeps moisture out of the electrical part at the top of the glass heater tube. The insulated lid goes on the coolerr top and the power wires for the pump and heater keep it slightly ajar.
I add a small quality of laundry grade chlorine bleach to keep algae at bay if I am going to run it for a few days continuosly.
If I have added bleach, I will not use the tempering water as rinse water.
Usually the cooler I use is a 'lunch box' sized one that allows me to warm 1L of dev, stop, bleach and fix for c-41 (yes, I home brew and split the blix into two steps). I slightly crack the bottle caps so the glass jars won't crack when the liquid and air inside the bottle expands , and then add tempering water at about 105F to the cooler. Heater and tank pump in, lid on, off for dinner, and by the time I have cleared the table and leaded the dishwasher the chems are all stable, up to temp, and ready to start processing.