it completely ok to keep session active when is needed - like in your case. For example jbpm console uses single session that is active all the time so there is no need to actually dispose it. Disposal of ksession is important if you have many instances of them.

Memory consumption will not be high as process instances are persisted in db when not executed like when being in wait state.

HTH

yes, it is important in that case as you would have many ksessions. So I would recommend for you to create some sort of mapping mechanism for the process instance and ksession so you can dispose the ksession as soon as possible (it reached wait state) and then use the right session to resume it like when completing task or signaling.

HTH

yes, you could do that but please note that you can't dispose it directly in the event listener as it is still using ksession and thus you would need to use transaction synchronization to dispose ksession after transaction has been completed. Take a look here as it might get helpful.

HTH