Eckhard Schnabel commenting on Acts 2:4:

The verb “fill”…is a more intense form…Luke uses the aorist indicative form…with a genitive of divine Spirit to designate “short outbursts of spiritual power/inspiration, rather than the inception of long-term endowment of the Spirit,” a fact that explains why a person might be “filled with the Holy Spirit” on many occasions while at the same time remaining “full” of the Spirit.

Schnabel, Acts, p. 115. [… represent Greek words I have left out due to font issues.]

Keeping a place for both types of Spirit filling is very important to healthy Christian practice. Personally, this is one of my main criteria when selecting a church. If a church does not have a grid for repeated Spirit fillings, meaning repeated Spirit empowerment as in the quote above, that church is going to be forced to do some things in their own natural strength. Talent and good principles will only take us so far. While it is true that God sometimes gives us certain graces without our seeking or even being open to them, his normal pattern is to act in response to prayer. If believers don’t have a vision for repeated fillings of the Spirit they are unlikely to ask God for them, or seek ministry from those who can pray for that.