Here it depends from your positioning. If you work in mass sector, the discounts are widespread and people are often waiting for them.
But if you work with the more sophisticated audience/higher level clients, discounts are not recommended. As in luxury segment are discounted only unpopular and useless goods which can not be sold. The price should be final. Here you selling your time and service - if you do three services instead of one, you will not win anything from it, it is not the same like selling goods when the more you sell the more profitable it is.
Sometimes it is better to give some additional service/present unexpectedly instead of giving discount. This works more effectively than discounts.