Well barrel life is not a HUGE deal. Plans are to get a custom barrel within the next year or so anyway.
That depends on how much you intend to shoot the rifle, how much rifle down time matters, and how much cash you can invest in barrels. Perhaps you should have the rifle made in a switch barrel configuration so that every few weeks you can swap out the barrels. Then again, if you shoot 100 rounds a year you might get 10 years out of your barrel. If a good barrel is now in the $600 range, you can add 60 cents to the cost of each round you fire, based on 1000 rounds of target grade accuracy in competition.
If all this sounds rather negative, well it is. There is simply no way to load a .264 magnum to extend barrel life to 5000 rounds. Barrel life can be mitigated by choosing the heaviest bullets you can find, by being cautious in your choice of powder, and by allowing plenty of cooling time between shots; so you might get 2000 rounds out of the barrel. Shooting in competition often involves time constrains, and at times requires your string to be fired very rapidly before conditions can change. This does nothing for barrel life. But when extending barrel life becomes the primary objective, your loads will not be as consistent or as accurate as when the same velocity is attained from a smaller cartridge.
Ballistically, the .264 or a 6.5-300 magnum quickly approaches the point of diminishing returns. If a .378 Weatherby for example was necked down to 6.5, despite it's huge powder capacity, it would produce no more velocity, and the standard belted magnum cases are not a huge leap ahead of either the 6.5-284 or the 6.5-06. The 6.5 magnums do only one thing well, and they do it little better and with less versatility than the smaller cased rounds.
When we are talking about long range target shooting, mostly we are shooting at known distances and quite frankly flat trajectory takes a back seat to accuracy. As long as you have enough adjustment in your sight, the actual drop at the target doesn't matter a damn. The same goes for wind drift, if you are good at doping the wind, whether you adjust for 1 minute or 3 doesn't much matter, and if you get it wrong you are out of the black in any case.
If we are talking about long range varminting, velocity and light bullets are the answer, but this combination from a .264 will have the barrel gone in a single summer. If long range big game hunting is your interest, many more rounds will be fired in load development than in the field, but the bullets from the .264 are too small and too light to produce the desired results when the ranges extend beyond a half mile on large game. This is the domain of the high capacity over .30 club.