Don't use capo. 
I think it's in the correct key.
Enjoy ;)

B               F#
HOW LONG WILL I LOVE YOU?
E          B                  C#m
AS LONG AS STARS ARE ABOVE YOU
B          F#
AND LONGER IF I CAN


B               F#
HOW LONG WILL I NEED YOU
E              B              C#m
AS LONG AS THE SEASONS NEED TO
B      F#
FOLLOW THEIR PLAN 

    E               C#m
    HOW LONG WILL I BE WITH YOU?
    F#                    B
    AS LONG AS THE SEA IS BOUND TO
    C#m  B    F#
    WASH UPON THE SAND

B               F#
HOW LONG WILL I WANT YOU?
E          B             C#m
AS LONG AS YOU WANT ME TO
B          F#
AND LONGER BY FAR   

B               F#
HOW LONG WILL I HOLD YOU?
E          B                   C#m
AS LONG AS YOUR FATHER TOLD YOU
B          F#
AS LONG AS YOU ARE

    E              C#m
    HOW LONG WILL I GIVE TO YOU?
    F#           B
    AS LONG AS I LIVE TO YOU
    C#m          B    F#
    AND HOW EVER LONG YOU SAY     

B               F#
HOW LONG WILL I LOVE YOU?
E          B                  C#m
AS LONG AS STARS ARE ABOVE YOU
B          F#
AND LONGER IF I CAN

B F# E B C#m B F#

B               F#
HOW LONG WILL I LOVE YOU?
E          B                  C#m
AS LONG AS STARS ARE ABOVE YOU
B          F#

B
END.