I have submitted a suggestion to Microsoft Connect which I would appreciate people voting for. The issue is that Microsoft Dynamics GP Fixed Asset Management only supports depreciation over a 99 year life; in the UK property/land can need to be depreciated over 125 years (or sometimes even longer).
As GP doesn't support this, clients are often reluctant to use the Fixed Assets module as they will have to handle the long-life assets in Excel and they commonly take the view that they might as well do all assets that way so that they are all stored in the same place.
Updating GP to support three character years would be of great benefit and allow assets to be depreciated over the correct life span. Please take a look and vote on this suggestion.