I work out of client's offices (I'm in IT, and visit 2 clients per day)
Sometimes I work in the server room. What's a server room? A closet, usually 6 feet by 10 feet, with 4 of those 6 feet being taken up by a rack of screaming servers and routers (take a loud desk fan, multiply x 50, and put next to your ear) and air conditioning to cool that space (imagine a NASA wind tunnel, and the temperature set to something like 15c)... and A desk. Where I need to work for 4 hrs at a time. I wear my leather jacked, and sweater, when it's +30c outdoors.
Sometimes there is no table at a server room, so I get put in someone's office. Boy are the owners of the office confused when they get there - but I was told to sit here? I've gotten moved to 3 different desks at a client in 4 hours before, because every person that they thought would be out was actually in that day (they were all off, but the boss decided to call a meeting and interrupt their vacations)
Sometimes I come to a client with a list of tasks delegated to 4 hours. The client then hands me a subsequent list for another 2 hours of work. I have to finish 6 hours worth of work in 5 hours (the last hour of which is my lunch - a lunch I don't get to eat since I have to be at the next client on time)
Today...
Manager: we need you to work at client X at 7:30 pm (after a full day of work) because that's when the client approved downtime.
Me: ok, I can do a bit of overtime. If you send another engineer with me, we can knock this out, and get it done by 10 PM. But I HAVE to be out at 10 pm, I have a 2-month old baby at home. If you can't get someone to help me, I can do it for 4 hours on my own, but it would have to be on saturday
Manager: ok, I'll ask the client
Manger sends email to the client: I asked the engineer, we're good for 7:30 tonight! Please approve this time
Client: we approve!
Me: Manager, did you get me another person to do this job with me?
Manager: oh, I can't get you anyone this late. But you can do this quick, right?
The job solo will be 4 hours, give or take. I'll be done at midnight. And I have a client I have to be at at 7 AM tomorrow. I live 1 hour away from both clients, so I'll be home at 1 AM, and I'll have to leave my house at 6 AM to drive to tomorrow's client.