I invested $44,449 in an S&P500 index fund over a period of 15 months. Its current market value is $43,596.

As someone who has adopted the buy and hold strategy, how long should I wait before adjusting/rebalancing/selling part of this fund?

I don't need funds at this time. I m trying to know how much time should be given to an S&P 500 index fund for it give considerable returns?

Thanks