I dont think you will ever get a good answer to this.
There are 3 big variables:
Original build quality - we know ducati have had some very poor and very good periods.
Quality of servicing - oil changes at the right time make huge differences to any engine
Riding style - infrequent but fast and furious will wear out any engine sooner than frequent but sensible
and all of these have huge ranges with ducatis - even a badly built ducati will last a long time with a careful owner, and even a really well cared for ducati will need high maintanance when ridden by a d1ck
