In the compatibility view sys.syscacheobjects the data type is NVARCHAR(17) though there are items such as 'Compiled Plan Stub' that are 18 characters in length. This causes them to show up truncated, as such using these (which I would argue not to use, though many books and reference articles still do) could cause results to not come back when searching for truncated items. If the data type was switched to NVARCHAR(50) the items would not be truncated.
This would bring it in line with sys.dm_exec_cached_plans which is a NVARCHAR(50).
Example: Compiled Plan Stub shows up as "Compiled Plan Stu"