Furball
Evil Scotsman
It helps in terms of winning the Ashes as well IMO. KP and Bell have played in 4 victorious series; Cook, Prior, Anderson, Swann and Broad in 3.This is a valuable point. It often takes time to feel you belong at a certain level. It's much easier to come into a settled side which can afford to give you time to adjust. Blokes like Hayden, Martyn, Langer and Ponting came into a side which was winning and settled, and could learn from the established players.
Currently Australia is trying to balance the need to develop certain players with the desire for short term results. It's less of an issue with the bowling, because there is genuine depth there and the physical requirements of that discipline means there will be some rotation between players. The batting is a different story though, with chopping and changing and moving between positions really leading to instability in the side. You get the impression blokes like Khawaja, Hughes, Cowan etc are playing for their spot every time they go out to bat. It's not a healthy mind set for inexperienced players.
Contrast that experience with Australia's, whose 2 most successful players are Clarke (1 series win, 4 defeats) and Siddle (14 Ashes Tests, 2 wins).