One of the most difficult questions faced by organizations is how to actually deploy the system. Should it a direct cut over deployment be attempted? It is the cheapest and most direct? Should the two systems be run in parallel?
And for how long? Is there a way to do a phased implementation?
Discussion of the issues and how does a company make a decision of which type of approach to take. Things that might be considered are:
Urgency of the new system in production
Experience and past performance of the development team
Complexity of the new system
Criticality of the new system (what is the cost of errors or failure?)