A story by Roger Hoogeveen:
Unicode Conversions are more and more requested by customers driven by SAP's strategy to support only unicode systems as of NetWeaver 7. For the project team unicode conversions may be real challenging as the next story might clarify. The total runtime of an upgrade and unicode conversion was approx. 1 year and a half in one of our situations.
The next part is about our experiences with unicode conversions and the possible scenarios. I hope that it clarifies the unicode conversion project and the possibilities for customers and partners to optimize the runtimes. [...]
You can read more in his blog post: https://blogs.sap.com/2009/02/17/experiences-from-unicode-conversions/