ModelJUnit Run Test for a period of time

I am performing some model-based testing on an application system, and I want to execute my tests for a specified duration of time (let's say for 15 minutes).

How can I achieve this, please?

So far, my tester looks like this:

final Tester tester = new GreedyTester(new AgentSystemModelTests());
tester.setRandom(new Random());
tester.buildGraph();
tester.addListener(new StopOnFailureListener());
tester.addListener("verbose");
tester.addCoverageMetric(new TransitionPairCoverage());
tester.addCoverageMetric(new StateCoverage());
tester.addCoverageMetric(new ActionCoverage());
tester.generate(500);
tester.printCoverage();