Making them the last stop in the adventure may do it. They may not be a good starting point. You may need to be already excited to derive pleasure from nipple stimulation.
Perhaps starting around your back, arms, ears or sides skin will get you "ready to rumble"?
Starting in an obvious erogenous zone is a very common mistake.
It is akin to hand-picking up the ball and dropping it in the winning pocket to win a billiards game. BIG YAWN!!!!!
It is the finer moments that make reaching the goal so special...