I've read somewhere around here that environmental temperature swings create problems for a PID-controlled E61 machine because the offset was established for a specific environment. In the winter our kitchen is usually 58 or 59F in the morning, high 60s during the day, sometimes 70. Does this translate into a 10F difference when the water hits the puck? If so, is there anything I can do to minimize this? Even in the summer the kitchen's temperature changes a lot. I generally keep the espresso machine on 24/7, although I don't see how that would make any difference.
Honestly I can't tell a difference between shots in the morning and shots in the afternoon, so maybe the answer to my question is, it's not a problem if I can't taste it in the cup.