StoneCut,
there is much debate on the ideal marinating time. i'm sure BIR's don't go above 24 hrs. i use a gas bbq to cook the tikka (breast cut in half lengthways, marinade, then 6-7 mins per side on a Skewer ie 4 side in total). this may have a bearing on it. i do see a difference between say 24hrs and 3 days - the chicken is far more tender. there is no change in the tikka taste between 3hrs and 3 days.
i also aim for a thick paste as i find this produces a more intense taste and stir the marinade at least once per day.
best wishes