I've successfully deployed this strategy in the past. I used to run a service off a personal server for a bunch of MUDs. Eventually I didn't want the responsibility of hosting some important infrastructure for them so I sent them the source code and instructions for how to set it up, but didn't hear back from the admins for months.

So I made everybody who used the service see a message saying "this service is retiring, please move it to your own infrastructure" before it would redirect to the actual service. I gradually increased it from 1 second to 30 seconds and eventually the admins set up the service on their own infrastructure.