I've worked at a couple "mid-sized" financial companies (i.e., not "tech" companies, but with a healthy need for various computer products and services) throughout my career where migration plans from one technology or provider to another were measured in years, and would sometimes get extended to the order of decades for larger migrations (e.g. moving core business functionality off a legacy mainframe system). A year or two notice that you'll need to migrate something important is really not feasible for a lot of businesses who would otherwise be very interested in outsourcing to a cloud provider.