Currently there are roughly 98.000 companies worldwide using Dynamics NAV. Of these companies 99.9% use a database with customisations done and 95% are different from all other NAV systems.
This was and is where NAV is strong.
This is a market of undocumented customised solution. It is a market of slow growth. As a consultant you can easily stick to one single enduser for a decade or longer. Simply because the real added value is knowing the customer.