They also run lean which makes them hotter. To date, with my own eyes I've seen one siezed and one bottom end failure on Bullet Sixty-fives that the owners ran on UK motorways for extended periods. One was a 2004, the other (I think) 2007.

Nikasil in this case is a bit of a red herring, it's a hardening process. A cast iron bore had to be made under size to allow for the wear. The engine started with a tight bore, was run in then lost compresion over the cylinders life. It always ran hot either due to friction or working harder to make the same power with the worn components. The nikasil bore is made the correct size (hopefully) and then keeps it for longer. This helps in that the fits are correct, so only the required amount of heat is produced, but it doesn't help an engine run at full power with no way to get rid of the heat except convention past the fins.

Yes there have been serious changes (in the oil circuit too), but are you saying the Electra/AVL will run 250 miles in under 4 hours day after day? No one seems to be able to give me a straight answer on that one as I can't find anyone using the newer Bullets except as weekend toys, running them just like the cast iron engines.

Yamaha XT's burn oil when used on the motorway, another pure aircooled design that simply can't get rid of the heat, it isn't restricted to the Enfield. BMW's, Harleys and Triumphs don't do it because you are only taking 25 HP out of a motor designed for 50-60 HP while the singles run full tilt. A Harley's biggest issue is cooling the rear cylinder at idle, hence the newer ones idle on the front cylinder only, again they simply can't get enough air to flow past where the heat is.

Apologies if I somehow denegrated your personal choice of bike, but there are designs much better suited to the motorway.

Andy