Lessons not learned by Taliban fighters

Yesterday's attack on Combat Outpost Margah in the Barmal district of Paktika province, only a couple of miles from the border with Pakistan, is not the first large-scale assault on this base.
In yesterday's attack around 70 insurgents - many of them foreign fighters, identified by their radio chatter prior and during the attack - were killed for no reported US casualties. Most of those killed died through accurate bombing from aircraft and artillery called in during the six-hour attack.
Compare that attack to an almost identical event that occurred at COP Margah on 30 October last year, when 60 US soldiers from Fox Company, 2nd Battalion, 506th Infantry came under attack in the night from a large number of insurgents, of whom around 80 were killed. Reports on that attack can be found here and here. 
The ferociousness of that encounter, one of the largest between US forces and insurgents in the last 10 years, can be gauged from the medals awarded afterwards: Fox Company soldiers received one Silver Star, three Bronze Stars, 12 Army Commendation Medals, two Purple Hearts and 10 Combat Infantrymen Badges.
And just a few weeks before the recent attack, on 7 October, Haqqani fighters launched a series of attacks on several US bases in the area, including Margah. According to one report, COP Margah itself was hit by 111 high explosive rockets plus mortars. Then, at 8am, as this official photo shows, an attempt was made to drive a truck bomb across flat ground straight into the base. It was stopped 50 yards short of the base when the driver was killed and the explosives ignited. 

Presumably in most of these cases the US had advance information about the attacks. But why, having been so comprehensively defeated at this location, did the Taliban/Haqqani fighters come back again and again?