diff --git a/src/osgEarthDrivers/engine_rex/EngineContext b/src/osgEarthDrivers/engine_rex/EngineContext
index 28656521ab..d1f77d27f3 100644
--- a/src/osgEarthDrivers/engine_rex/EngineContext
+++ b/src/osgEarthDrivers/engine_rex/EngineContext
@@ -76,9 +76,7 @@ namespace osgEarth { namespace REX
 
         const TerrainOptionsAPI& options() const { return _options; }
 
-        ProgressCallback* progress() const { return _progress.get(); }
-
-        double getExpirationRange2() const { return _expirationRange2; }
+        ProgressCallback* progress() const { return _progress.get(); }        
 
         ModifyBoundingBoxCallback* getModifyBBoxCallback() const { return _bboxCB.get(); }
 
@@ -104,8 +102,7 @@ namespace osgEarth { namespace REX
         const SelectionInfo&                  _selectionInfo;
         osg::Timer_t                          _tick;
         int                                   _tilesLastCull;
-        osg::ref_ptr<ProgressCallback>        _progress;    
-        double                                _expirationRange2;
+        osg::ref_ptr<ProgressCallback>        _progress;
         osg::ref_ptr<ModifyBoundingBoxCallback> _bboxCB;
         const FrameClock*                     _clock;
         osg::ref_ptr<TextureArena>            _textures;
diff --git a/src/osgEarthDrivers/engine_rex/EngineContext.cpp b/src/osgEarthDrivers/engine_rex/EngineContext.cpp
index ff5e682c24..53bd8a8c5f 100644
--- a/src/osgEarthDrivers/engine_rex/EngineContext.cpp
+++ b/src/osgEarthDrivers/engine_rex/EngineContext.cpp
@@ -49,7 +49,6 @@ EngineContext::EngineContext(
     _tilesLastCull(0),
     _clock(clock)
 {
-    _expirationRange2 = _options.getMinExpiryRange() * _options.getMinExpiryRange();
     _bboxCB = new ModifyBoundingBoxCallback(this);
 
     // create a bindless texture arena and set it to automatically
diff --git a/src/osgEarthImGui/TerrainGUI b/src/osgEarthImGui/TerrainGUI
index fab3ad6e6f..b9e1be4000 100644
--- a/src/osgEarthImGui/TerrainGUI
+++ b/src/osgEarthImGui/TerrainGUI
@@ -84,6 +84,8 @@ namespace osgEarth
                     return;
                 }
 
+                static unsigned u32_one = 1;
+
                 auto options = _mapNode->getTerrainOptions();
 
                 if (ImGuiLTable::Begin("terraingui"))
@@ -111,8 +113,7 @@ namespace osgEarth
                         visible_cb->setVisible(terrain_visible);
                     }
 
-                    static int max_max_lod = -1;
-                    static unsigned u32_one = 1;
+                    static int max_max_lod = -1;                    
                     unsigned max_lod = options.getMaxLOD();
                     if (max_max_lod < 0) max_max_lod = max_lod;
                     if (ImGuiLTable::InputScalar("Max LOD", ImGuiDataType_U32, &max_lod, &u32_one, nullptr, "%u"))
@@ -152,6 +153,36 @@ namespace osgEarth
                         engine->dirtyTerrainOptions();
                     }
 
+                    // Expiration options
+                    ImGui::Separator();
+                    unsigned int minExpiryFrames = options.getMinExpiryFrames();
+                    if (ImGuiLTable::InputScalar("Min Expiry Frames", ImGuiDataType_U32, &minExpiryFrames, &u32_one, nullptr, "%u"))
+                    {
+                        options.setMinExpiryFrames(minExpiryFrames);
+                        engine->dirtyTerrainOptions();
+                    }
+
+                    float minExpiryTime = options.getMinExpiryTime();
+                    if (ImGuiLTable::InputFloat("Min Expiry Time", &minExpiryTime))
+                    {
+                        options.setMinExpiryTime(minExpiryTime);
+                        engine->dirtyTerrainOptions();
+                    }
+
+                    float minExpiryRange = options.getMinExpiryRange();
+                    if (ImGuiLTable::InputFloat("Min Expiry Range", &minExpiryRange))
+                    {
+                        options.setMinExpiryRange(minExpiryRange);
+                        engine->dirtyTerrainOptions();
+                    }
+
+                    unsigned int maxTilesToUnloadPerFrame = options.getMaxTilesToUnloadPerFrame();
+                    if (ImGuiLTable::InputScalar("Max Tiles to Unload", ImGuiDataType_U32, &maxTilesToUnloadPerFrame, &u32_one, nullptr, "%u"))
+                    {
+                        options.setMaxTilesToUnloadPerFrame(maxTilesToUnloadPerFrame);
+                        engine->dirtyTerrainOptions();
+                    }
+
                     if (GLUtils::useNVGL())
                     {
                         unsigned maxTex = options.getMaxTextureSize();
@@ -269,7 +300,7 @@ namespace osgEarth
                         _sample = _sampler->getSample(mp);
                         _ax = _x, _ay = _y;
                     }
-                }
+                }                
 
                 ImGui::Separator();