There are certain situations I associate with smoking,being on a plane isnt one of them I(only flew on a smoking flight once) so I dont have a problem with TATL flights, until a year or so ago you could smoke at LHR and I still miss that, by and large I manage fine, after about 5 hours I do fancy a smoke but ignore it. when I only flew occasionally I used nicotine gum but it really gives you heartburn and stomach pain so I give it a miss now.