It is common to omit some verses in #hymns to save time; normally, this is fine. However, there are some hymns that this doesn't work well for, although it is still common. One type of hymn that should be sung completely is hymns that follow a trinitarian pattern, with each verse being about one person of the Trinity. For example, “Be Thou Exalted” by Fanny Crosby has one verse about the Father, one about the Son, and one about the Holy Spirit:
Verse 1 Be Thou exalted, forever and ever, God of eternity, Ancient of Days! Wondrous in majesty, perfect in wisdom, Glorious in holiness, fearful in praise.
Refrain Be Thou exalted by seraphs and angels, Be Thou exalted with harp and with song; Saints in their anthems of rapture adore Thee, Martyrs the loud hallelujahs prolong.
Verse 2 Be Thou exalted, O Son of the Highest! Gracious Redeemer, our Savior and King! One with the Father, co-equal in glory, Here at Thy footstool our homage we bring. [Refrain]
Verse 3 Be Thou exalted, O Spirit eternal! Dwell in our hearts, keep us holy within; Lead to Thy home in the life everlasting, Open its portals and welcome us in. [Refrain]
Omitting verses takes away from the point of a trinitarian hymn more than it does with most hymns, so it should be avoided with hymns following this format.