diff --git a/streamable/iterators.py b/streamable/iterators.py
index 38f1e5e..8e821b3 100644
--- a/streamable/iterators.py
+++ b/streamable/iterators.py
@@ -149,7 +149,7 @@ def __next__(self) -> U:
                 self._current_iterator_elem = noop_stopiteration(iter)(iterable_elem)
 
 
-class _GroupIteratorInitMixin(Generic[T]):
+class _GroupIterator(Generic[T]):
     def __init__(
         self,
         iterator: Iterator[T],
@@ -161,12 +161,20 @@ def __init__(
         validate_group_interval(interval)
         self.iterator = iterator
         self.size = size or cast(int, float("inf"))
+        self.interval = interval
         self._interval_seconds = interval.total_seconds() if interval else float("inf")
         self._to_be_raised: Optional[Exception] = None
         self._last_group_yielded_at: float = 0
 
+    def _interval_seconds_have_elapsed(self) -> bool:
+        if not self.interval:
+            return False
+        return (
+            time.perf_counter() - self._last_group_yielded_at
+        ) >= self._interval_seconds
+
 
-class GroupIterator(_GroupIteratorInitMixin[T], Iterator[List[T]]):
+class GroupIterator(_GroupIterator[T], Iterator[List[T]]):
     def __init__(
         self,
         iterator: Iterator[T],
@@ -176,13 +184,8 @@ def __init__(
         super().__init__(iterator, size, interval)
         self._current_group: List[T] = []
 
-    def _interval_seconds_have_elapsed(self) -> bool:
-        return (
-            time.perf_counter() - self._last_group_yielded_at
-        ) >= self._interval_seconds
-
     def __next__(self) -> List[T]:
-        if not self._last_group_yielded_at:
+        if self.interval and not self._last_group_yielded_at:
             self._last_group_yielded_at = time.perf_counter()
         if self._to_be_raised:
             e, self._to_be_raised = self._to_be_raised, None
@@ -198,11 +201,12 @@ def __next__(self) -> List[T]:
             self._to_be_raised = e
 
         group, self._current_group = self._current_group, []
-        self._last_group_yielded_at = time.perf_counter()
+        if self.interval:
+            self._last_group_yielded_at = time.perf_counter()
         return group
 
 
-class GroupbyIterator(_GroupIteratorInitMixin[T], Iterator[Tuple[U, List[T]]]):
+class GroupbyIterator(_GroupIterator[T], Iterator[Tuple[U, List[T]]]):
     def __init__(
         self,
         iterator: Iterator[T],
@@ -215,11 +219,6 @@ def __init__(
         self._is_exhausted = False
         self._groups_by: DefaultDict[U, List[T]] = defaultdict(list)
 
-    def _interval_seconds_have_elapsed(self) -> bool:
-        return (
-            time.perf_counter() - self._last_group_yielded_at
-        ) >= self._interval_seconds
-
     def _group_next_elem(self) -> None:
         elem = next(self.iterator)
         self._groups_by[self.by(elem)].append(elem)
@@ -244,11 +243,12 @@ def _pop_largest_group(self) -> Tuple[U, List[T]]:
         return largest_group_key, self._groups_by.pop(largest_group_key)
 
     def _return_group(self, group: Tuple[U, List[T]]) -> Tuple[U, List[T]]:
-        self._last_group_yielded_at = time.perf_counter()
+        if self.interval:
+            self._last_group_yielded_at = time.perf_counter()
         return group
 
     def __next__(self) -> Tuple[U, List[T]]:
-        if not self._last_group_yielded_at:
+        if self.interval and not self._last_group_yielded_at:
             self._last_group_yielded_at = time.perf_counter()
         if self._is_exhausted:
             if self._groups_by: