The concept of compound interest does not mean that you have to buy a fund for 30 years to compound interest, but that you can continue to invest for 30 years, with an average annual income, that is, compound interest.

As for whether to change after three years, the key is to see if there is any problem with the fund you invest in, and the income obviously lags behind the market average. If so, you should consider changing it. If not, there is no need to change it.

The ranking of funds always takes turns. It is not necessary to pursue funds according to rankings, but to consider whether the relative performance in a period is acceptable.