For the chain RIC constituents using batch subscriptions from time to time, if the old constituents (since the chain constituents are changing from time to time) are not unregistered via the handles, only new registering towards the new constituents are issued, will that be a problem considering the watch-list and application running performance?
If you do not unregister items that you no longer require, then may continue to receive events+data for these other constituents (unless they have expired themselves). Also, they will continue to use memory.
If the chain constituents do not change too often, then you could say the above may not a big issue - especially if the application is shut down and restarted regularly.
However, if the application is running 24x7 all year round and/or the chain changes often - then the additional unwanted events+data, as well as memory usage, could start impacting the performance.
I always recommend the customer unregister any items they are no longer interested in. Obviously, this requires some additional coding effort on the part of the developer - but should not be too onerous.