having been guilty of it numerous times throughout my racing career, i believe that doing tempo during the race season is bad training strategy, and a recipe for training moderately, aka making your hard rides not hard enough and your ez rides too hard ... unless it's H.O.P. style (hard tempo with sprints/accelerations every 3 to 5 minutes, which in actuality is a neuromuscular power workout that forces you into an AP/NP in L4).
disclaimers/ymmv