Is there any impact/effects in using an older version of JMeter? Since in the JMeter best practices wiki page, it is advised not to use the versions that are older than 3 versions of the current one.
Provide more input in this regard, since am using an older version which is more than 3 versions of the current one.
Help needed.
It depends on Test Plan nature and what Test Elements you're using. Normally newer JMeter releases contain bug fixes and performance improvements so theoretically you can achieve higher throughput using newer JMeter version.
There is JMeter Performance evolution across versions wiki page where you can see the trend of improving JMeter performance across versions so if the throughput is critical for you in terms of load test lab costs - it's better to consider upgrade asap.
On the other hand if your test works fine you can continue using earlier JMeter version in order to keep consistency of the test results for regression testing purposes. Moreover, if your test relies on JMeter Plugins - some of them simply might stop working with newer JMeter version due to JMeter API change.
So for existing project it is OK to keep previous JMeter version given potential cost of migration, but for the new one it is highly recommended to stick to the latest JMeter version. In both cases make sure to follow JMeter Best Practices and recommendations from the 9 Easy Solutions for a JMeter Load Test “Out of Memory” Failure article.
For migration, always read release notes in order to know what to do: