To say 10 min per block is only statistically right.
You might see several blocks mined in a row in a few minutes but in another time none for an hour.

Height    Age    Transactions    Total Sent    Relayed By    Size (kB)
346427    29 minutes    46    1,773.59 BTC    BTC Guild    21.74
346426    29 minutes    217    607.58 BTC    F2Pool    119.97
346425    32 minutes    772    6,959.44 BTC    BTC Guild    416.73
346424    46 minutes    320    1,659.23 BTC    F2Pool    155.84
346423    51 minutes    1010    8,987.83 BTC    F2Pool    507.12
346422    1 hour 10 minutes    614    6,597.82 BTC    KnCMiner    417.55