It says "be filled" in the present tense indicating we are supposed to be filled continually. It is not a one time event
And yet Ephesians 5.18 does (!) and not only says it but commands it
And yet the result of being continually filled is associated with Spirit inspired worship as we see from the verse that follows v19.
*What is clear throughout the NT is that believers who are already indwelt with the Holy Spirit still experience other works and manifestations of the Holy Spirit. The Spirit will "fall" on them, and inspire spontaneous outbursts of praise and worship, or lead them to prophesy. The Spirit will guide them in evangelism efforts. The Spirit will warn and direct them in dreams and visios. We see believers operating in the gifts of the Spirit. Believers are told to fan into flame the gift received by the laying on of hands. Believes are warned not to quench or grieve the Spirit. And yes, the Spirit is involved in sanctification too and the gifts of the Spirit.
*What is unmistakable is that unlike today with our rather forensic, academic theological analysis of how the Spirit does this and that, we see in the NT that the Spirit is not an academic matter, but a real, tangible empowering Presence in the life of believer. The Spirit is not simply received and that's it (as if the Spirit now just passively resides in us), but the Spirit is God's empowering Presence actively at work in the lives of believers throughout our lives. For Paul, the Christian life is all about life in the Spirit
*So, yes, we agree there is only one initial indwelling, but that is not the end but the beginning of the Spirit's work in our lives, ethically but also in other ways. However one wants to phrase it, anointing, infilling, falling, refreshing, etc... I often suspect we don't have the vocabulary to adequately describe God's supernatural work... But whatever words we use, however one tries to describe it, what seems clear in the NT is that believers didn't simply receive the Spirit in an academic way, but in a real, tangible, empowering, life changing transformative way that continued after their first reception of the Spirit.