This is a subject many different people have different opinions on, including manufacturers.  Basically, "ball death" is when the coverstock absorbs an amount of oil that it makes the ball lose some effectiveness, in terms of grabbing the lane, which can lead to loss of carry, even on pocket hits.  It typically happens more with particle coverstocks, but reactives can be succeptible also.  Also the higher the load of particles the more easily it can happen.  The best thing you can do is to clean your ball regularly, most manufacturers reccommend after each time you bowl.  There are some who have said they have never had a ball die on them.  I've had a few, almost all particles.  The Eraser Pearl Particle is a light load I believe which should last you quite a while if you take care of it.  Buy some cleaner and clean by hand after you bowl, or take it in to the pro shop occassionally and have him/her do it for you.  There is a lot more that can be said on this, but I don't want to get into what companies balls last longer, and how they say to maintain their balls and all of that.  Take care of your ball, and it will take care of you.