Migrating to the most up-to-date versions of software is important for a number of reasons: getting automatic or easy-to-implement critical security upgrades and patches, sticking with officially supported versions and avoiding the problems inherent in sticking with something out of date. You want the most recent, tested and most stable versions of business-critical software to save yourself from not just inefficiencies but also everything from lock-in to ballooning maintenance costs.
As you might already know Varnish Cache Plus is a Varnish Plus product that is built on the top of the open source project Varnish Cache. Varnish Cache is usually a little ahead with regard to versioning because it may have some experimental features.
When does migrating become business critical?
Varnish Cache 3.0 (the open source project) was released back in 2011 while Varnish Cache 4.0 made its debut in 2014. Since then, we’ve seen Varnish Cache 4.1.x appear, and now, the most recent, Varnish 5.0, which was only recently released.