Well, the Agile approach is to break them down into smaller things that can be accomplished in under 1,000 hours.
"There's nothing that can be accomplished in a single chunk taking more than a 1,000 hours that will produce a system with a manageable and maintainable level of complexity unless it is broken into smaller, well-defined and loosely-coupled components," perhaps.
"There's nothing that can be accomplished in a single chunk taking more than a 1,000 hours that will produce a system with a manageable and maintainable level of complexity unless it is broken into smaller, well-defined and loosely-coupled components," perhaps.