Major designs like the Countach and Diablo ran for a very long time. Minor changes have lasted 2-6 years ie hard to make a general statement from that. The Diablo ran from calender year 1990 (mostly 1991 models although there were a few 1990 VINs) through to 2001. Approx dates are:

2WD Diablo ran 1990-1994.
VT Diablos ran 1993-1999.
SV Diablos ran 1995-1999.
Diablo Roadsters 1996-2000 (1999 model year).
Variable Valve Timing 5.7 Diablo engines 1998-1999.
Diablo 6 litre ran 2000-2001

The Muci started its run in 2001. Already you hear talk of the bigger engine Murci and an SV Murci so within a year or two the current spec Murci would be gone I would suspect.

-mick