For decades past, churches were open all day on Nov 2. so people could visit the cemetary, then the church MULTIPLE TIMES. On Monday even the Novus Ordo churches were open for this purpose in my city.
From the 1957 Raccolt page xvi (under Canons)
b) In order to gain plenary indulgences which are to be obtained as often as the prescribed work is performed, and for which a visit to some church is enjoined, it is necessary and sufficient to say at least six times at EACH VISIT Our Father, Hail Mary and Glory be to the Father. (S.P. Ap., July 5 1930; Acta Ap. Sed., vol. xxii, p.363)
On page 472 number 590 under devout excercises for the faithful departed for Nov 2 it again stresses "as often as they visit a church"
Multiple visits are supposed to be a sacrifice.
However the New Regulations on Indulgences states on page 26 "Yes; only one plenary indulgence can be gained on All Souls' Day".