One quick Google search brought up Pedro's garage article. Link below. His bottom line is quoted.
These numbers apply to M96 and M97 engines of Boxster, 996 and Cayman with those engines. Failure rates are per year, as I understand it from the class action suit. I will add that failure rates increase when driven and revs rarely go over 3k. Infrequent oil changes also cause problems. Minimally, oil changes should be done each year if driven 5k or fewer miles and at least every 5k miles. I do mine at 3k and drive it in a spirited manor every time out ;-))
Don't let dirty oil sit over the winter. Store with fresh oil.
And yes, from the Gen2 motors of '09 and on, the IMS issue went away.
Kaboom! Technical Article by Pedro
(*) We now believe that the failure rates vary according to the model year and the way it is driven, or not. The lowest failure rates (1-3%) are the ’05 and newer cars with the larger, non-removable single-row IMS bearing. The ’97 – ’00 cars with the double-row bearing have failure rates of 4-7% and the ’00 – ’05 have the highest of all failure rates, just around 10%. These rates seem to climb when cars are not driven for extended periods and seem to decrease when cars are tracked regularly.