Don't retry if remaining time isn't enough.

src/Microsoft.Azure.EventHubs/Primitives/RetryExponential.cs

@@ -49,12 +49,6 @@ namespace Microsoft.Azure.EventHubs
             TimeSpan retryAfter = this.minimumBackoff.Add(TimeSpan.FromMilliseconds(nextRetryIntervalSeconds * 1000 + nextRetryIntervalMilliseconds));
             retryAfter = retryAfter.Add(TimeSpan.FromSeconds(baseWaitTimeSecs));
 
-            // Don't retry if remaining time isn't enough.
-            if (remainingTime.TotalSeconds < Math.Max(retryAfter.TotalSeconds, ClientConstants.TimerToleranceInSeconds))
-            {
-                return null;
-            }
-
             return retryAfter;
         }
 

src/Microsoft.Azure.EventHubs/Primitives/RetryPolicy.cs

@@ -95,7 +95,16 @@ namespace Microsoft.Azure.EventHubs
                 }
             }
 
-            return this.OnGetNextRetryInterval(clientId, lastException, remainingTime, baseWaitTime);
+            var retryAfter = this.OnGetNextRetryInterval(clientId, lastException, remainingTime, baseWaitTime);
+
+            // Don't retry if remaining time isn't enough.
+            if (retryAfter == null || 
+                remainingTime.TotalSeconds < Math.Max(retryAfter.Value.TotalSeconds, ClientConstants.TimerToleranceInSeconds))
+            {
+                return null;
+            }
+
+            return retryAfter;
         }
     }
 }