The Book of Acts is filled with prayer meetings; every forward thrust the first church made was immersed in prayer. Take another look at the church at Pentecost. They prayed ten days and preached ten minutes and three thousand people were saved. Today we pray ten minutes and preach ten days and are ecstatic if anyone is saved.
You may notice that the Acts 2 account of Pentecost doesn’t mention a ten day prayer meeting. The number comes from knowing the ascension of Jesus Christ was 40 days after His resurrection (Acts 1:3) and that Pentecost was 50 days after it (Pentecost was, by definition, 50 days after the passover, which was when Jesus rose from the dead. Leviticus 23:16 refers to Pentecost). This leaves a ten day gap. At the start of those ten days, we read the disciples “all continued with one accord in prayer and supplication, with the women and Mary the mother of Jesus, and with His brothers” (Acts 1:14). In Acts 2:1 we read “When the Day of Pentecost had fully come, they were all with one accord in one place”, and the idea that the intervening period was spent in prayer and supplication is an assumption.