Did the idea of 108 times come from Gurbani? I will check on that. I think not. I know that in some panths and sects of Sikhism the number of times for a mantra or a kriya is mentioned and one increases incrementally -- 6, 11, 23, I think the next one is 56, and so forth -- I am not an expert on this. But the time of simran is a very individual thing and depth of simran is more important according to other teachers.