I think parenting makes you tired. Especially with two. DS1 weaned when I was pg with DS2 and I didn't feel any less tired than when he was bfing. The same thing happened when DS2 weaned - parenting two boys was still every bit as tiring. Personally I don't think bfing had any impact on this.

As Barb says, your body also used nutrients more efficiently when you are bfing. I need regular blood tests for high iron, and my GP was always commenting on the fantastic nutrient levels that I had while bfing.