SQL Server 2008R2 DBCC CheckDB never finishing
There is a very interesting post on DBCC CHECKDB on SqlPerformance, Minimize impact of checkdb. This will give you several ideas, like testing your backup on another server (therefore offloading the charge), using several options (you can experiment with PHYSICAL_ONLY for example). 

As CHECKDB is making a big use of tempdb, this you check how things are going on for this database? Is it on separate disk?