Prior to the release of Microsoft Dynamics NAV 2015, an upgrade was a tremendous project that required hundreds (sometimes thousands) of hours to bring you to the latest version.
The upgrade required a lot of time because of modifications done in your database; essentially, the less you modify, the faster the upgrade. In fact, if you need to upgrade from versions prior to Microsoft Dynamics NAV 2013, you may see similar estimates during a new implementation.
Microsoft Dynamics NAV can be used with no customization at all, but that's almost unheard of. That's like buying a Ferrari and only driving it at 25 miles per hour. Once users discover the power of Microsoft Dynamics NAV and how flexible the software is, they will want to make changes so that they have a competitive edge in their industry. It's like the users suddenly discover the power...
