IMO your rates are low, but I don't know what is normal for your area.
That aside I would not lower the hourly rate.
If you really won;t to give them a break I suggest writing the bill at your regular rate than at the bottom give them a "Frequent Customer Discount" (or some such wording) of whatever you feel is appropriate off the total.
In this way that see that they got a break and will not be expecting a lower hourly rate next time.
Take that for what it is worth....I do not run a business.
