DOC Document partial template caching aggregates recommendation

docs/en/02_Developer_Guides/08_Performance/00_Partial_Caching.md

@@ -107,6 +107,13 @@ template render.
 
 [/warning]
 
+[warning]
+If you use the same aggregate in a template more than once, it will be recalculated every time
+unless you move it out into a separate
+[controller method](../templates/partial_template_caching/#cache-key-calculated-in-controller).
+[Object Caching](../templates/caching/#object-caching) only works for single variables and not for chained expressions.
+[/warning]
+
 
 ## Purposely stale data