I've just begun cycling 'seriously' again after a break of oh, let say 20 years. I find, this time around, I'm much more interested in using (what remains of) my 'motor' more efficiently ie. consistent cadence enabled by appropriate gear choices. At times, this requires shifting both the front and rear derailures. Now the question. Is it advisable to shift both front and rear derailures simultaneously? I've 'discovered' this technique and it seems to work well. The shifts are smooth and nothing suggests it's any harder on the equipment than shifting one, then the other derailure. Still, I have nagging doubts that I'm promoting premature wear and tear of my transmission. For whatever it might matter, my bike is equipped with Shimano 105 levers and derailures. I'd appreciate suggestions/experiences on this subject. Thanks!