This is a good question. I'd love to see more people comment on this one. I don't really know...but I heard that it is not necessary to do decline bench with every chest workout. Maybe every other chest day or even once a month. Also depending on the training split, ie chest/tri's together. Dips hit the lower pecs as do push-downs...some more than others depending on form.

This might be old thinking...I thought the best mass builder for chest is basic flat bench with barbell whereas dumbells help strength.

Blah Blah Blah...I really just should have said "bump!"