Sorry cyccomute, I meant I didn't "need" front carriers to carry any gear. I can see that if you have so much gear you need four panniers, then all that gear on the back may affect your balance
You aren't quite getting it. Everything that I carry on a bike could fit in the rear panniers. I'm not in need of space. But putting the load over the front wheel makes a large difference in the way that the bike handles. I've used just front bags or two small front and rear bags. I've also toured with just rear bags. The front only or front/rear split is a fast improvement over rear only.