Document flash_write_interval (#1381)

components/esphome.rst

@@ -276,6 +276,35 @@ This option behaves differently depending on what the included file is pointing
    AND compiled into the binary. This way implementation of classes and functions in header files can
    be provided.
 
+.. _preferences-flash_write_interval:
+
+Adjusting flash writes
+------------------------
+
+.. code-block:: yaml
+
+    # Example configuration entry
+    preferences:
+      flash_write_interval: 1min
+
+- **flash_write_interval** (*Optional*, :ref:`config-time`): Customize the frequency in which data is
+  flushed to the flash. This setting helps to prevent rapid changes to a component from being quickly
+  written to the flash and wearing it out. Defaults to ``1min``.
+
+As all devices have a limited number of flash write cycles, this setting helps to reduce the number of flash writes
+due to quickly changing components. In the past, when components such as ``light``, ``switch``, ``fan`` and ``globals``
+were changed, the state was immediately committed to flash. The result of this was that the last state of these
+components would always restore to its last state on power loss, however, this has the cost of potentially quickly
+damaging the flash if these components are quickly changed.
+
+A safety feature has thus been implemented to mitigate issues resulting from the limited number of flash write cycles,
+the state is first stored in memory before being flushed to flash after the ``flash_write_interval`` has passed. This
+results in fewer flash writes, preserving the flash health.
+
+This behavior can be disabled by setting ``flash_write_interval`` to ``0s`` to immediately commit the state to flash,
+however, be aware that this may lead to increased flash wearing and a shortened device lifespan!
+
+For ESP8266, :ref:`esphome-esp8266_restore_from_flash` must also be set to true for states to be written to flash.
 
 .. _esphome-changing_node_name: