I just want to make clear I could be wrong, but I am sharing what I understood till now.
Jo cheez sirf knowlegde lai aa, te learn karan lai aa. oh sahayad ik baar learn kar lo taa baar baar repeat karan di lor ni. Like reading history, understanding algorithms do not need repetition.
Now lets go to other things, like music, loving your mom/dad/sibling or lover. We do that again and again coz these things needs repetition coz we either enjoy it or gets a piece of mind and some rest at our soul.
Same holds for Gurbani Path, if you do it as love to lord and you do it for peace of mind, a food for your soul then it requires repetition. So we need to do it daily.
If it is about learning Granths, Vedas, Qurans then one can keep read it once and leave them.
NOW As per my knowledge, even Gurbani asks sikhs to do repetitions..
"Simro simar simar sukh paavo......."
"ek do jeevo lakh hoye, lakh hove lakh bees, lakh lakh gerda aakhiye Ek naam Jagdish..."
"Sab tude passo mangde NIT KAR ardas"