In most companies, ITSM tool selection is a big deal. Whatever you choose, you’re stuck with it for at least the next three years, and realistically even longer. You're probably going to have to change internal processes to fit in with how the tool works, and maybe even change the team. 

Given that IT tools have such an impact on the organizations that purchase and use them, a key part of any purchase decision should be how you can replace it - either because of the advent of improved technology, changing business requirements, or perhaps the tool simply not meeting its original objective. No tools are used forever, yet few organizations have a strategy for replacement at the time of purchase and even fewer make it one of their decision criteria. 

This model also applies where tools are to be integrated - it should be possible to replace different ITSM tools and continue to use the others - otherwise that organization has lost flexibility to adapt to a changing world.

Improvements to technology and work patters are making various tools obsolete, as well as other aspects such as security compliance, vendor consolidation and so on - all of which means that a flexible tool strategy can be a big positive for most companies. 

For example, ACME Corporation may have embraced virtualization throughout their data center - not just virtual servers, but virtual networking, storage etc - and their existing monitoring tools may not be up to this task. It should be possible for them to swap out these monitoring tools for equivalents which do fully support these environments without massive expense, and also possible to leave other tools that are meeting their needs such as service desks, Business Service Management tools and so on.  

When making tool and vendor selections, companies should consider:

• How easy would it be to remove this tool and replace it with an equivalent?
• What other ITSM functions that need to be integrated with this one? Can this tool integrate with not only the tools I have, but the leading alternatives?
• If I were to remove this tool, what would be the impact on other tools that I have in my environment?
• Will this tool force me to be so custom in a particular area of process, staffing, skill set or technology that it would make removal impossible?

These are not hard and fast rules and should be evaluated against other criteria such as necessary and desirable functionality, the vendor, other services and so on - but it is important to at least consider replacement even at purchase time. After all, three years really isn't such a long time.