In-flight. That's the trouble I sometimes see with IT architecture. Rarely are we given the luxury of rolling out a new model. Instead we have to rebuild or replace components of complex architecture while it's still in use. I like the analogy of replacing the aircraft engine while the plane is in-flight. A pretty impossible task I would say.
That's why building the architecture on a solid foundation is so important. Of course that is easier said than done in the real world. The real world is full of demanding clients, tight deadlines, tight budgets and applications/infrastructure that have to be up almost all the time. Of course the other big problem is that we are not perfect. Sometimes the right architecture at first is not always the right architecture later on. Ever remodel a house? Sometimes your needs change beyond what the house is capable of providing. Sometimes it's as simple as adding a room while other times it calls for more drastic measures like tearing out foundations, walls and other large things (not to mention the portable toilet that sits out front of your house for months).
The big promise of a SOA style of architecture is the potential to handle change better. If done semi-correctly, large destructive remodeling should not be as frequent or necessary. How to do it semi-correctly? That's the million dollar question. Let's explore that more in future conversations.