I mean this is why you do these projects on two different timelines: The internal timeline and the external timeline.
Externally you communication: Different announcements each month, final notices at T+5M, System will be deleted at T+6M, data will be lost at that point and so on.
Internally (at least at work) such a timeline is more that at T+6M, we cut access to the systems. Afterwards, systems not accessed for 2-4 weeks are removed periodically and the hard removal is planned for T+9M. Customer support and account managers can manage if systems need to be accessed. If a customer needs the system for a longer time, they can, but then they pay for it. Entirely with all necessary infrastructure, not renting a few licenses on the system.
Call it a bit callous, but this allows our customer support to appear nice and in control. And it leaves the customer happy and relieved that we have left some slack and leeway. But they've been shaken and woken up and can get to migrating.
The biggest challenge here is to stay on it and to not allow customers to become complacent again. This can be done by e.g. limiting the reactivation time to a week or so so they have to get on it.
Yep, and in certain in house situations it's best to keep a backup around for ~13 months in case there's an obscure business process that only gets done once a year. (I'm aware that some people reading that sentence are going to go wtf at the idea that that's anybody's problem except whoever didn't tell you said business process even existed, but if it's a sufficiently critical finance or HR thing it tends to rapidly become everybody's problem so I like to have options)
Agree absolutely wrt complacency, I believe I asked for less than a week because I actively preferred a situation where I had to get on it immediately.
Externally you communication: Different announcements each month, final notices at T+5M, System will be deleted at T+6M, data will be lost at that point and so on.
Internally (at least at work) such a timeline is more that at T+6M, we cut access to the systems. Afterwards, systems not accessed for 2-4 weeks are removed periodically and the hard removal is planned for T+9M. Customer support and account managers can manage if systems need to be accessed. If a customer needs the system for a longer time, they can, but then they pay for it. Entirely with all necessary infrastructure, not renting a few licenses on the system.
Call it a bit callous, but this allows our customer support to appear nice and in control. And it leaves the customer happy and relieved that we have left some slack and leeway. But they've been shaken and woken up and can get to migrating.
The biggest challenge here is to stay on it and to not allow customers to become complacent again. This can be done by e.g. limiting the reactivation time to a week or so so they have to get on it.