When I read Acts ch2 it reads that it was an event orchestrated by God thru his holy spirit to demonstrate his approval of this select group of people. The tongues spoken of are plainly the ability to speak the said languages of the people that were in attendance as a witness to them that ordinary folk who could not normally speak the languages of the foreign Jews and proselytes ,could now by gods gift do this to the amazement of some in attendance ,and yet some just thought they were drunk because they just simply did not understand the languages being expressed or the message being given by the people given the gift on that occasion, or the exuberance expressed by such a miraculous gift not before seen.
After all what were the things spoken of ,and why is it later spoken of as not wise to speak in this manner unless someone was there to interpret. Ones who claimed to have this gift that I have spoken to over the years put more emphasis on the languages used are the languges of angells ,but when shown Acts they go into diversion mode when confronted by the actual scripture quoting the languges spoken at Pentacost.
I've known many ,and was told by them that many who claimed to have this gift today,including themselves actually did drugs ,fornicated etc- when challenged about this they would go into cognitive dissonance mode not unlike JW's when challenged about the crap they believe from their own literature which proves to be false.
My ex-wife one day in field service with a group was confronted by a man using a "tongue" in the street ,when she challenged him to explain what the said it was the usual language of angells stuff ,but then she asked where is your interpretter to benefit the group from what he just uttered. He said he did'nt have anyone ,so she asked him then whether he made the mistake or the Holy spirit? If he made the mistake then how then was he able to speak in the language of angells?
That's the way to cut thru the Pentecostal bullshit!
As regards the timing of the gifts and how long they should last I would venture to say they only lasted as long as the contemporary people of the Pentecost time lived in the sense that the end of the Jewish system finished in a physical sense by the destruction of Jerusalem in 70 CE. Seems reasonable to me to conclude then that the gift of tongues had run it's course by that time ,achieving what it was meant to ,the physical evidence that gods spirit had shifted to the christian congo.
I'm here only using the reasoning available from the bible and real world experiences ,not searching the internet with what this or that scholar from this or that century says.