Darren,
It'll take a couple of weeks for your machines to reach ambient temperature.
But once they do, everything becomes a lot more stable, as there will be like storage radiators all over the shop and when you touch a machine, you don't recoil back because of the cold.
Mine has been on a fair while now with a first walk in temp of 14 deg C, and it is soon up to 17 or 18 once the machines start running.
In my shop, it is t-shirts all year around.
All that for less than a penny an hour during the winter months.
John