When developing architectures for an organization, a good recommendation is to make incremental deliveries at regular intervals instead of a complete architecture covering everything after a year or two.
Architecture work is often very fuzzy and the exact deliveries are seldom specified due to an unknowns as-is situation and unclear future. When the architecture maturity is low is it sometimes hard for the sponsor to know what what he needs, what he gets and how the work is done.
This is why I would suggest a more iterative or agile approach to architecture.
It's very common that the architecture initiative runs in parallel with a large program, even if the method says that the architecture should be done beforehand. In this case, you have to delivery something at an early stage to support the program and improve continuously as times go by, otherwise the program runs circles around the architecture initiative.
My suggestion is therefore to make architecture in 6-8 weeks projects, with bi-weekly deliveries of some views at certain levels of abstraction.