Hi Thorsten, It is very difficult to predict how quickly this issue will be seen, since it depends on many factors, including the number of FDB deletions and MAC moves.
You may monitor 'show memory process hal' output periodically to see memory utilization. If HAL memory utilization is rapidly increasing, then you really need to upgrade soon.
We recommend that you upgrade as soon as possible, if you are running EXOS 16.1.4.2