Just to clarify my earlier comments a bit more: We frequently DO raise the traveller well above the centerline for windward work. My comments above were discussing the idea of bringing the boom across the fore-'n'-aft centerline.
Occasionally we will bring the boom above the centerline, but only when we want to slow the boat by deliberately over-trimming (for instance, when sidling slowly up through a crowded anchorage under sail preparing to drop the anchor.)
Jeff's note above suggests some people do as you do with positive results, so maybe there are variations in boat design and rig geometry that make it advantageous to do so? Live and learn.