I'm an assistant GM at a Mcdonalds so I guess I'll explain the shake machine thing.
Mcdonalds shake machines have to enter heat mode. To keep the shake mix sanitized it heats up to 160 degrees, holds it for a few hours then cools down. This HAS to be done once every 24 hrs or the machines simply won't run. 24hr Mcdonalds usually do this sometime at night, or early morning. The last 24 I worked at did it from 2am to 4am or so. Non 24 hr mcdonalds have it go into heat mode when the store is closed. Honestly, if your Mcdonalds shake machine seems to be down quite a bit for repair and maintainence, take it as a good sign. I've asked shake machine repair people just how bad some of those machines get and it's truly disgusting.\
Honestly, if someone comes in late night and wants ice cream, go them. That's 100x easier than making 15 double cheese at 10:30.