I find the same kind of creep can happen at the office, too. Many colleagues end up leaving at 8 PM or later [0] because they have to do this one more thing or someone shows up with just a quick question to ask.
However, I realize that for some people, who have a harder time saying no for whatever reason, it's easier to have a hard, external excuse. "Sorry, I need to catch my train, so I don't have to sleep here" works less well when you're already home. But I think that in both cases it's very important to set boundaries and stick to them.
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[0] Our workdays are normally 9 AM to 6 PM.
That's still an office paid by your company, with all the benefits that go to the company.
The company I work for before opening a new office for their employer has to provide:
- security
- daily cleanings
- insurances for all the people working there
- reception
- authentication and authorization (badge readers etc.)
- secure connectivity and storage
- water, beverages, sometimes a cantine if the office is big enough.
That's by contract (at least my contract).
If they are really going through the route of paying for your coworking they should sign a contract, which means a lot of bureaucracy and most of all it would force the employer to always use the same space for at least a few years.
So the better way is to ask for a pay rise to pay it by yourself.
If you can pull it out.
Saying this after many, many years of remote working, where the boundaries between work and personal life blurred so far they became practically indistinguishable. (yay 24/7 "DevOps" culture :/)