Should you create subprojects?

A GTDer asked: I am using the GTD Outlook Add-In software. Should I create subprojects?

Coach Kelly: I personally don’t use the subproject feature of software. For me, everything is just a Project. But if you do decide to use it, it can be a nice way to sort major components of a large project. For example, let’s say you are getting married. You could have “Get married” as the project that you track, however, there would be many, many
steps that would fall under that. Some people would choose to create subprojects for each of the major components, such as:

Project =
Get Married

Subprojects =
Rehearsal Dinner

I’d say it’s an optional feature in the Add-In, not required. Only use it if it helps you. Don’t use that feature if it seems confusing or more complicated than you need. [Addendum: this is my universal feedback for people on creating your system. Use as many features as you need, but as few as you can get by with.]