diff --git a/optimas/explorations/base.py b/optimas/explorations/base.py
index 9b9d0bb1..802e58ec 100644
--- a/optimas/explorations/base.py
+++ b/optimas/explorations/base.py
@@ -31,14 +31,16 @@ class Exploration:
         The generator used to suggest new Trials.
     evaluator : Evaluator
         The evaluator that will execute the Trials.
-    max_evals : int
+    max_evals : int, optional
         Maximum number of trials that will be evaluated in the exploration.
-    sim_workers : int
-        Number of parallel workers performing simulations.
+        If not given, the exploration can run indefinitely.
+    sim_workers : int, optional
+        Number of parallel workers performing simulations. By default, 1.
     run_async : bool, optional
-        Whether the evaluators should be performed asynchronously (i.e.,
+        Whether the evaluations should be performed asynchronously (i.e.,
         without waiting for all workers to finish before staring a new
-        evaluation). By default, True.
+        evaluation). This is useful when the completion time of the
+        evaluations is not uniform. By default, False.
     history : str, optional
         Path to a history file of a past exploration from which to restart
         the new one. By default, None.
@@ -71,9 +73,9 @@ def __init__(
         self,
         generator: Generator,
         evaluator: Evaluator,
-        max_evals: int,
-        sim_workers: int,
-        run_async: Optional[bool] = True,
+        max_evals: Optional[int] = np.inf,
+        sim_workers: Optional[int] = 1,
+        run_async: Optional[bool] = False,
         history: Optional[str] = None,
         history_save_period: Optional[int] = None,
         exploration_dir_path: Optional[str] = "./exploration",
@@ -120,7 +122,9 @@ def run(self, n_evals: Optional[int] = None) -> None:
             sim_max = remaining_evals
         else:
             sim_max = min(n_evals, remaining_evals)
-        exit_criteria = {"sim_max": sim_max}
+        exit_criteria = {}
+        if np.isfinite(sim_max):
+            exit_criteria["sim_max"] = sim_max
 
         # Get initial number of generator trials.
         n_trials_initial = self.generator.n_trials
diff --git a/tests/test_exploration_resume.py b/tests/test_exploration_resume.py
index 1dda4df7..d32c43ca 100644
--- a/tests/test_exploration_resume.py
+++ b/tests/test_exploration_resume.py
@@ -42,7 +42,7 @@ def test_exploration_in_steps():
         evaluator=ev,
         max_evals=30,
         sim_workers=2,
-        exploration_dir_path="./tests_output/test_template_evaluator",
+        exploration_dir_path="./tests_output/test_exploration_steps",
     )
 
     # Run exploration in several steps.
@@ -59,6 +59,51 @@ def test_exploration_in_steps():
     assert exploration.history["gen_informed"][-1]
 
 
+def test_exploration_in_steps_without_limit():
+    """
+    Test that an exploration runs correctly when doing so in several steps
+    without a limit on the maximum number of evaluations.
+    """
+    # Define variables and objectives.
+    var1 = VaryingParameter("x0", -50.0, 5.0)
+    var2 = VaryingParameter("x1", -5.0, 15.0)
+    obj = Objective("f", minimize=False)
+
+    # Define evaluator.
+    gen = RandomSamplingGenerator(
+        varying_parameters=[var1, var2], objectives=[obj]
+    )
+
+    # Create template evaluator.
+    ev = TemplateEvaluator(
+        sim_template=os.path.join(
+            os.path.abspath(os.path.dirname(__file__)),
+            "resources",
+            "template_simulation_script.py",
+        ),
+        analysis_func=analysis_func,
+    )
+
+    # Create exploration.
+    exploration = Exploration(
+        generator=gen,
+        evaluator=ev,
+        sim_workers=2,
+        exploration_dir_path="./tests_output/test_exploration_steps_no_limit",
+    )
+
+    # Run exploration in several steps.
+    steps = [3, 4, 10, 5]
+    for step in steps:
+        exploration.run(step)
+
+    # Check final state.
+    assert exploration._n_evals == len(exploration.history)
+    assert exploration._n_evals == gen.n_trials
+    assert exploration._n_evals == sum(steps)
+    assert exploration.history["gen_informed"][-1]
+
+
 def test_exploration_resume():
     """Test that an exploration correctly resumes from a previous run."""
     # Define variables and objectives.
@@ -87,7 +132,7 @@ def test_exploration_resume():
         evaluator=ev,
         max_evals=40,
         sim_workers=2,
-        exploration_dir_path="./tests_output/test_template_evaluator",
+        exploration_dir_path="./tests_output/test_exploration_steps",
         resume=True,
     )
 
@@ -103,4 +148,5 @@ def test_exploration_resume():
 
 if __name__ == "__main__":
     test_exploration_in_steps()
+    test_exploration_in_steps_without_limit()
     test_exploration_resume()