This is often pretty easy (depending on your circumstances) for a first child, and we mostly followed it for our first. (There was a little screen time before she got to 2 but only low intensity shows on a regular full-sized TV - still her only screen time several years on, but with more choice from her).
With a second it's practically impossible. We'd need extra childcare (and more floorspace where we live!) to trap him in a different room while the first is watching TV. Taking TV away from the first would be very hard (you're right that it's hard to withdraw once it's routine) but also not something I'd want anyway.
I'm not convinced that it necessarily expands out once it has a foothold. We have a pretty well defined TV time (before dinner) and it's easy to say "yes you can watch that show ... when it's next TV time".
With a second it's practically impossible. We'd need extra childcare (and more floorspace where we live!) to trap him in a different room while the first is watching TV. Taking TV away from the first would be very hard (you're right that it's hard to withdraw once it's routine) but also not something I'd want anyway.
I'm not convinced that it necessarily expands out once it has a foothold. We have a pretty well defined TV time (before dinner) and it's easy to say "yes you can watch that show ... when it's next TV time".