Hi Tom,
The Greeting Length for a Call Handler is determined by the COS of the person recording the Greeting, so that is what will need to be changed. Have a look;
Class of Service Greetings Settings
The class of service greetings setting specifies the maximum length of greetings.
Subscribers > Class of Service > Greetings Page
Field Considerations
Maximum Greeting Length in Seconds
Select the recording length allowed to subscribers assigned to this COS for recording greetings.
The range is 1 to 999 seconds; the default is 90 seconds.
If enabled, a warning tone will sound before the maximum greeting length is reached.
From this doc;
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_administration_guide_chapter09186a008014f9da.html#1057646
Hope this helps!
Rob