Do you think that indices should change frequently or less often?

You are absolutely right that it does raise the issue of index consistency. Let us look at some interesting statistics. In last 25 years, Nifty has seen a total of 180 changes. On the other hand, the Dow Jones Industrial Average (DJIA) saw just 60 changes in 92 years.

So, there is a huge gap in the level of consistency. In comparison to the Dow, the Nifty surely looks far from consistent. Now, why is consistency important? Unless the index is relatively more consistent over time, it becomes very tough to be comparable across time periods.

Now look at Nifty returns. Nifty-50 gave CAGR returns of 9.5% in last 25 years. But with all the tweaks and changes, it is not too clear whether the index portfolio that has gone through so many changes would have justified the switch costs. Food for thought!