I dunno.
Why would you?
If you are happy and are using the entire bar and life is good... leave it be.
If you feel cramped and the need to stretch, or if you are very concerned about aerodynamics, or if you feel you get more power and happiness from your glutes by having more hip flexion, I guess you could lower the bars or toss in a longer reach stem.
But really, if you feel good, leave it be.