Create all the objects (cylinders) you're using to make the holes, select them all and perform a 'combine' on them. Now you should have two objects - the main sponge and your cylinders. Now, perform your boolean and it should work. This is typically how you would create things like holes in automotive disc brakes, for example, that have numerous amounts.
Originally posted by Mayastatic
Booleans do not work for more than 10 holes, after that it erases my hole mesh, the typical boolens problem!