I am not concerned with the cost of the extra electricity required to run the machine 24x7.

However, I have found that leaving the machine on for long periods every day accelerates the hardening of washers, gaskets and seals (yes, this is anecdotal evidence only). Not just the portafilter gasket but also e61 valve washers and the OPV seat. While these parts are not expensive, they are a pain in the rear to replace. I don't feel the convenience is worth the inconvenience of performing maintenance more often.

I use a heavy duty timer to turn on my machine in the morning and I turn it off myself after I pull the last shot of the morning.