Remember, you can check Paschale Solemnitatis on this site, among many on the internet.
107. This sacred period of fifty days concludes with Pentecost Sunday, when the gift of the Holy Spirit to the Apostles, the beginnings of the Church and the start of her mission to all tongues and peoples and nations are commemorated. (Cf. General Norms for the Liturgical Year and the Calendar 23)
And so Pentecost crowns Fifty Days, rather than initiates a period of eight.
The prolonged Pentecost Vigil is recommended:
Encouragement should be given to the prolonged celebration of Mass in the form of a Vigil, whose character is not baptismal as in the Easter Vigil, but is one of urgent prayer, after the example of the Apostles and disciples, who persevered together in prayer with Mary, the Mother of Jesus, as they awaited the Holy Spirit.*
*It is possible to combine the celebration of first Vespers with the celebration of Mass as provided for in the General Instruction of the Liturgy of the Hours, n. 96. In order to have a more profound knowledge of the mystery of this day, it is possible to have several readings from Holy Scripture, as proposed in the Lectionary. In this case, after the collect the reader goes to the ambo to proclaim the reading. The psalmist or cantor sings the psalm, to which the people respond with the refrain. Then all stand and the priest says: Let us pray, and after a short silent pause, he says the prayer corresponding to the reading (for example, one of the collects for the ferial days of the seventh week of Easter).
Evening Prayer plus an extended Liturgy of the Word would make for a delicious evening of liturgy: a fitting celebration of the forty-ninth evening after the Vigil.