How important is maintaining the starter temp? It's sitting around 70 now, didn't want to bother keeping the flask in a water bath or anything over the 24 hours.
The needed time for a starter is also depending of the room temperature. It is not needed to control the temperature for a starter.
Last time I made a starter I used my CO2
production sensor system. In the following screenshot you can see the temperature rise of the starter during its time on the stir plate.
The light yellow curve is the ambient temperature and the red curve is the temperature of the 1 liter starter. You can see the rising of the temperature from 22 degrees C to 25 degrees C. (In the beginning this sensor was on the ground)
The purple curve is the CO2 production in time. When the production of the CO2 of the starter decreases I placed the starter into the fridge. A few days later I used the starter and the yeast was in very good condition because the CO2 production of that badge started in 4 hours.