Keisei & Tokyo Subway (outside Narita)

Hello! I'm travelling to Japan in March 2015. I arrive at Kansai (KIX) airport and leave from Tokyo (NRT).

We will spend the entire last week in Tokyo (7 days). The first 2 days we will be covered by the JR Pass (day trips to Kamakura and Nikko).

Looking into options from Tokyo Center to Narita Airport, I stumbled upon the Keisei Skyliner + Subway combo tickets.

http://www.keisei.co.jp/keisei/tetudou/skyliner/us/value_ticket/subway...

Specially the 3 day subway ticket + Skyliner. It would cost 3500 JPY, and would include 3 full days of subway (both companies).

However, if I'm not mistaken it can only be bought at the Narita Airport :( so... it would be useless for me?

Some friends are visiting Japan a few months before my trip, would it be possible to ask them to buy the tickets for me, despite being a few months later?? Or do they have to be used the same day?

I also read about the simple 1-2-3 tokyo subway (combined, 2 companies) costing 1500 JPY for the 3 day ride.

However, the same problem arises, I belive I can only buy it at the Airport (I read mentions of it being available in "Travel agencies outside Tokyo" but I'm unsure if that's really possible and doable being a foreigner).

Thanks

Please consider carefully if subway pass makes sense at all - for getting around within Tokyo, you often need to use combinations of JR local trains and subways, so that subway passes often do not pay off. Rather than that, I would get a Suica or Pasmo prepaid card, which can be used on either JR or non-JR (including both subway companies), and top up as needed.