I have a large old tree which did very badly last year compared to previous years. This year it is absolutely loaded, with branches drooping to the ground. Good point about late flowering bringing more insects, I had not thought of that (though we heard at the time that there were many bee and insect losses because of the inconsistent harsh weather).
Apart from the lower branches, it is impossible to thin. It is a very late maturing apple (a dual purpose Charles Ross, according to Brogdale apple day) but I always pick steadily as soon as they are large enough, and process and freeze, using this magnificent little machine:
http://www.youtube.com/watch?v=rzq9pd3iUTA (but I wind mine much faster than she does).
It saves hours of work. I got mine in Tasmania and it is quite robust - I bought a Lakeland one to give away, and it was disappointingly flimsy, but I am sure there are better models around. The apple comes out in spiral form, and if you slit it down the side you have neat apple rings for drying.
One problem about a late apple is that birds and wasps and some sort of rot gradually thin them out until by the time they are sweet in October, there are not so many of them. That is why I make sure to start stashing them away from late August. I regard the windfalls as helpful compost.