Re: Maintenence window, gosh how quaint
With any luck, the sales staff who sold the client something as something it is not in the first place.
I can think of at least one such coke-hoover* where I work who has cost the company several weeks unpaid development time in the last year, due to not-entirely-truthful statements made to clients. this has included me having to learn, and make changes to, a product, which in any reasonable universe would have been end-of-lifed at least a decade ago.
*metaphorically speaking, I'm sure none of my colleagues would ever touch the Bolivian Marching Powder, and any behavioural traits that might be associated with such are purely coincidental.