Looking in the source code, it is 720 blocks:
static const int64 nTargetTimespan = 0.5 * 24 * 60 * 60;
static const int64 nTargetSpacing = 60;
static const int64 nInterval = nTargetTimespan / nTargetSpacing;
nInterval is number of blocks before difficulty retargets.
I was just looking at nTargetTimespan >_>
I feel like an idiot.
I think those bits were mentioned in shake's cloning guide, so i assume he must've known to change it in doubloons as well.