A few notes:
1- What difference does it make setting landing conf 3 instead of full just at the limit altitude (500 or 1000 ft depending non VMC or IMC)? I think it is negligible with respect to any flighttime not at idle during the approach due to a non optimum TOD and descent. Not to mention the much greater saving of a "more thant optimum descent" such as going low on profile, then "ready for base" and fly some 6 to 10 less NM.
2- does the fuel saving outweights the extra fuel, engine wear and brakes wear due to the extra speed? (in the ecuation of kinetic energy, speed goes squared: a 3% extra speed means a 6% extra energy).
3- I rarely fly conf 3, and i don't like it because i am not used and with light weights thrust is almost idle. And i feel a tailstrike is more likely to occur to me, which is scary.
4- Maybe it is better just to delay flap full until shortly before 1,000 ft, instead of the procedural, when flaps 3, select flaps full
5- a lot of bits of fuel saved can make a big saving in a big airline
6- just one incident (tailstrike) can waste years of saving
7- i would like captains to encourage me to fly conf 3 approaches, but they don`t like it. So i dont like it when a conf 3 is recommended for windshear and gusty winds, because aside from the conditions I have to deal with an unusual attitude and thrust.
8- Extra time taxiing is also a factor, which will occur in many airfields if you use more rwy length. For instance at FCO after landing you may just let it roll with reverse idle to the end. conf 3 that day is fine. But in other airports, the extra speed will be paid either by extra reverse and braking or extra taxi time. Time is more expensive than just fuel.
9- To what extent are experts the experts who say that conf 3 landings save money?