Erik Darling explains why index tuning is typically not a one-shot process:
For many people, index tuning means occasionally adding an index when there’s a report about a slow query. Those indexes might come from a query plan, or from the missing index DMVs, where SQL Server stores every complaint the optimizer files when it thinks an index might make a query better.
Sure, there are some people who think index tuning means rebuilding indexes or running DTA and checking all the boxes, but I ban those IP addresses.
The prudent choice, of course. Read on for Erik’s thoughts on the subject, which are quite good.