I fly long haul all the time. The problem is if we are not in the galley, we don't always hear the chime, but the light should show, and we will go and see what it is that you need. I disagree with the person who thinks that it is rude. Whilst I am more than happy for people to come and stretch their legs and pick up what they want, it is not always possible on night flights when there are people asleep between the the passenger or the aisle. There is, there always must be one person minimum not on rest at any time. That is what they are there for, whilst my ex-colleague is absolutley correct, we hope that we will never have to put it into use.
We all know the sort that use them bell as though they were summoning the parlour maid, we can deal with that as well. Indeed, one poor soul could not distinguish betwen the bells as the design is sometimes awkward. She kept wondering why we kept comming and was so embarrassed, although we assured her that she had no need to be. Give me people like her any day!