Change record status: 
Project: 
Introduced in branch: 
7.x
Description: 

The $user->cache and {session}.cache fields are no longer being used to enforce per-user minimum cache lifetimes, and will be removed in 8.x.

This should only affect modules that replace the core caching system.

Impacts: 
Module developers
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done

Comments

Support for $_SESSION['cache_expiration'][$bin] has been removed completely from 8.x in http://drupal.org/node/730060.