I've never bothered with de-tipping, since a few fly on the tip don't seem to do much harm. It's when the fly decide they fancy the whole plant that they do damage, and then they develop all over the place so de-tipping will make no difference.
The fly extract the sap, take out the goodness, and poo sugar syrup - they don't use all the sugar - and that's why ants (and sometimes bees) like them. If you ever come across honeydew honey (lime, for instance), it's concentrated essence of aphid poo, vomited up by bees. Lovely!
