My current work (we sell office supplies) is evaluating options for a replacement for their core ERP system that handles over a billion dollars in orders a year.
After a long competition, we're down to SAP and Microsoft as the final two contenders.
The SAP guys gave a talk for the general tech-heads at the company on what the current generation of SAP stuff does.
One of the more interesting parts of the talk was regarding the SAP core systems (general ledger, etc etc). It's been around for a few years now (most of the new shiny features are around the services and apps outside the core) and SAP's next release of their core systems is due in 2013.
The takeaway comment from the SAP expert giving the talk (and he was not at all a sales droid, showing actual clue) was that businesses (especially management) doesn't like upgrading.
SAP surveys of their client base suggest the ideal/desired upgrade path (patch-levels aside) for "stable" business types is...
"We want to upgrade once every 8-12 years, on a Saturday afternoon"