diff --git a/ProjectPlugins/CodexPlugin/MarketplaceAccess.cs b/ProjectPlugins/CodexPlugin/MarketplaceAccess.cs
index 2b90af41..8944d95c 100644
--- a/ProjectPlugins/CodexPlugin/MarketplaceAccess.cs
+++ b/ProjectPlugins/CodexPlugin/MarketplaceAccess.cs
@@ -105,13 +105,13 @@ namespace CodexPlugin
         public TimeSpan? PendingToSubmitted => contractSubmittedUtc - contractPendingUtc;
         public TimeSpan? SubmittedToStarted => contractStartedUtc - contractSubmittedUtc;
         public TimeSpan? SubmittedToFinished => contractFinishedUtc - contractSubmittedUtc;
-        public TimeSpan? StartedToFinished => contractFinishedUtc - contractStartedUtc;
 
         public void WaitForStorageContractSubmitted()
         {
             WaitForStorageContractState(gracePeriod, "submitted", sleep: 200);
             contractSubmittedUtc = DateTime.UtcNow;
             LogSubmittedDuration();
+            AssertDuration(PendingToSubmitted, gracePeriod, nameof(PendingToSubmitted));
         }
 
         public void WaitForStorageContractStarted()
@@ -121,6 +121,7 @@ namespace CodexPlugin
             WaitForStorageContractState(timeout, "started");
             contractStartedUtc = DateTime.UtcNow;
             LogStartedDuration();
+            AssertDuration(SubmittedToStarted, timeout, nameof(SubmittedToStarted));
         }
 
         public void WaitForStorageContractFinished()
@@ -129,11 +130,12 @@ namespace CodexPlugin
             {
                 WaitForStorageContractStarted();
             }
-            var currentContractTime = DateTime.UtcNow - contractStartedUtc!.Value;
+            var currentContractTime = DateTime.UtcNow - contractSubmittedUtc!.Value;
             var timeout = (Purchase.Duration - currentContractTime) + gracePeriod;
             WaitForStorageContractState(timeout, "finished");
             contractFinishedUtc = DateTime.UtcNow;
             LogFinishedDuration();
+            AssertDuration(SubmittedToFinished, timeout, nameof(SubmittedToFinished));
         }
 
         public StoragePurchase GetPurchaseStatus(string purchaseId)
@@ -173,18 +175,31 @@ namespace CodexPlugin
 
         private void LogSubmittedDuration()
         {
-            Log($"Pending to Submitted in {Time.FormatDuration(PendingToSubmitted)}");
+            Log($"Pending to Submitted in {Time.FormatDuration(PendingToSubmitted)} " +
+                $"( < {Time.FormatDuration(gracePeriod)})");
         }
 
         private void LogStartedDuration()
         {
-            Log($"Submitted to Started in {Time.FormatDuration(SubmittedToStarted)}");
+            Log($"Submitted to Started in {Time.FormatDuration(SubmittedToStarted)} " +
+                $"( < {Time.FormatDuration(Purchase.Expiry + gracePeriod)})");
         }
 
         private void LogFinishedDuration()
         {
-            Log($"Submitted to Finished in {Time.FormatDuration(SubmittedToFinished)}");
-            Log($"Started to Finished in {Time.FormatDuration(StartedToFinished)}");
+            Log($"Submitted to Finished in {Time.FormatDuration(SubmittedToFinished)} " +
+                $"( < {Time.FormatDuration(Purchase.Duration + gracePeriod)})");
+        }
+
+        private void AssertDuration(TimeSpan? span, TimeSpan max, string message)
+        {
+            if (span == null) throw new ArgumentNullException(nameof(MarketplaceAccess) + ": " + message + " (IsNull)");
+            if (span.Value.TotalDays >= max.TotalSeconds)
+            {
+                throw new Exception(nameof(MarketplaceAccess) + 
+                    $": Duration out of range. Max: {Time.FormatDuration(max)} but was: {Time.FormatDuration(span.Value)} " +
+                    message);
+            }
         }
 
         private void Log(string msg)
diff --git a/Tests/CodexTests/BasicTests/MarketplaceTests.cs b/Tests/CodexTests/BasicTests/MarketplaceTests.cs
index e4e1797b..7cff4aa5 100644
--- a/Tests/CodexTests/BasicTests/MarketplaceTests.cs
+++ b/Tests/CodexTests/BasicTests/MarketplaceTests.cs
@@ -83,10 +83,6 @@ namespace CodexTests.BasicTests
 
             AssertBalance(contracts, client, Is.LessThan(clientInitialBalance), "Buyer was not charged for storage.");
             Assert.That(contracts.GetRequestState(request), Is.EqualTo(RequestState.Finished));
-
-            AssertDuration(purchaseContract.PendingToSubmitted, 30, 1, nameof(purchaseContract.PendingToSubmitted));
-            AssertDuration(purchaseContract.SubmittedToStarted, purchase.Expiry.TotalSeconds, 30, nameof(purchaseContract.SubmittedToStarted));
-            AssertDuration(purchaseContract.SubmittedToFinished, purchase.Duration.TotalSeconds, 30, nameof(purchaseContract.SubmittedToFinished));
         }
 
         private void WaitForAllSlotFilledEvents(ICodexContracts contracts, StoragePurchaseRequest purchase, IGethNode geth)
@@ -121,11 +117,5 @@ namespace CodexTests.BasicTests
             var slotHost = contracts.GetSlotHost(request, contractSlotIndex);
             Assert.That(slotHost?.Address, Is.Not.Null);
         }
-
-        private void AssertDuration(TimeSpan? span, double expectedSeconds, int tolerance, string message)
-        {
-            Assert.That(span.HasValue, "IsNull: " + message);
-            Assert.That(span!.Value.TotalSeconds, Is.EqualTo(expectedSeconds).Within(tolerance), message);
-        }
     }
 }