Well, I've succeeded in configuring the timeout through ActivitiEngineConfiguration class:
<java>
AsyncExecutor asyncExecutor = new DefaultAsyncJobExecutor();
asyncExecutor.setAsyncJobLockTimeInMillis(20 * 60 * 1000);
asyncExecutor.setDefaultTimerJobAcquireWaitTimeInMillis(20 * 60 * 1000);
processEngineConfiguration.setAsyncExecutor(asyncExecutor);
</java>
Works fine. Martin, why would you advise against this practice? Will it affect engine in a negative way? Do you suppose to create some servlet, which will be accessible through REST API and return call results as signal variables, so service task will just send a REST request and won't wait for the response?