Using third party libraries for productivity gains in software development is common.  Unfortunately, along with the library's functionality we also import its bugs. Some of them get fixed in subsequent releases.  So, to upgrade or not to upgrade, this is the question. I am interested in learning from experiences when upgrading to a newer version of the library was desirable, but after a cost/benefit analysis the conclusion was that upgrading was not a good solution in the grand scheme of things. I am interested in finding out what forces influence the decision towards not upgrading.  
When would you choose *not* to update a third-party library to a newer version?
libraries;software updates;third party libraries;maven;3rd party
The short answer is that the new version could introduce new bugs, as Robert Harvey mentioned in the comments.To be honest, I think you are approaching this the wrong way.  In my experience, the better approach is to default to sticking with the version you have.  Presumably, your team has already tested the version you use and how it integrates with your system.  If not, then your clients have.Sure, when a new version comes out, your team should see if it addresses any bugs you have encountered, provides features you could take advantage of, or improves overall performance.  Only after running it through testing again should you actually start using it.The problem with approaching upgrades as something which is done by default and only halted if someone finds a problem is that it is too easy to become lax on the vetting process.  Eventually, this will bite you when a new version introduces new issues.If you stick with the version you have, you know that the overall system behavior will not change.