Lexmark C752 Technical Reference page 239

userdiskpercent
returns a (zero) on the stack.
Errors: stackoverflow, invalidaccess
waittimeout
queries the current value for the WaitTimeout user parameter. An integer is
returned on the stack:
disabled
seconds
This operator is equivalent to executing the following PostScript emulation
sequence:
currentuserparams /WaitTimeout get
Error: stackoverflow
4-56
PostScript