I’ve been praying the 15 decade rosary for some time now, once I understood through my studies that it was the rosary presented by our Holy Queen Mother to St. Dominic, so any additions since then are not what was divinely given.
I pray the 15 decade rosary the way St. Louis Montfort taught us, available online at http://www.philomena.org/rosarydemontford.asp and be sure to add the prayer our Holy Mother taught us at Fatima, available online at https://www.thoughtco.com/the-fatima-prayer-542631 .
Today, I timed how long it took to say the full fifteen decades in one sitting, 40 minutes.
Here is one great place (I got mine here) to get 15 decade rosaries, http://www.sistersofcarmel.com/custom-15-decade-rosaries/
This article from Tradition in Action makes the case for the 15 decade rosary superbly.
“While driving home from the chapel last week, I was praying the Joyful Mysteries of the Rosary. My plan was to pray the Sorrowful Mysteries in the afternoon and the Glorious Mysteries in the evening before going to bed. For many years, I had simply prayed the five decades designated for the day in order to fulfill Our Lady’s request at Fatima that her children pray the Rosary every day for the Consecration of Russia and the peace of Christ in the world. At least I thought that was the nature of her request. More on that misunderstanding will be clarified momentarily.
“Then, one evening in December, one of our parishioners in Southern California mentioned to me that he prays the whole Rosary every day because if Our Lady said that Francisco would go to Heaven only after praying many Rosaries, and he died at the tender age of ten, then how many more would we have to pray to get there! That struck a chord with me.
“I now believe that it is good to pray the entire Rosary daily for three reasons.
“Our Lady asked for the full Rosary
“The first reason is that when the Virgin Mary asked us at Fatima to pray the Rosary every day, she was not asking for five decades. She was asking for fifteen. When Our Lady says “Pray the Rosary,” she is speaking of what has been termed her Psalter, a word referring to the Book of Psalms, which contains one hundred and fifty Psalms of David. From the time of St. Dominic, “Mary’s Psalter” was the 150 Hail Marys. In 1569 St. Pope Pius V, himself a Dominican, issued an apostolic letter establishing the fifteen-decades as the official Church-authorized Rosary.
“For some, if not many, it may seem like too much to ask, given so many other daily responsibilities, to pray the whole Rosary. They will say that even one of the Mysteries, that is, a set of five decades, is difficult.
“I would respond that each one of us is awake at least fifteen hours of the day. Some are awake a few hours longer, but for the sake of argument, we will use the figure fifteen hours. Yes, it would be very nice to get nine hours of sleep at night! If each of us prayed one decade of the Rosary each waking hour, which amounts to five minutes out of every sixty of our day, we would pray the entire Rosary every day.
“Oh sure, some days we could get tied up for two to three hours at a time at work and subsequently “fall behind” in this commitment. But then there is always the ride home, which for most people is more than five to ten minutes, so decades can be made up for in the drive. It does take a little bit of planning ahead and at times those unexpected circumstances do arise. Hard working mothers who are home with their children also face varying circumstances. But, as the old saying goes, “Where there is a will, there is a way.”
“A special efficacy in praying the 15 decades
“This leads to the second reason why I believe this is a very important commitment for us as Catholics to make. Our Lady said that she had obtained from God a special efficacy to be attached to the praying of the Rosary so that there was nothing that we could request from her that we could not obtain through the daily Rosary. If we believe our Mother when she speaks to us, then this statement alone should fill us with great confidence and the desire to ask Our Lady’s intercession for our spiritual and temporal welfare by praying the Rosary. It is like what Jesus said to His Apostles on the night before He died, “Whatever you ask for in My Name, it will be given to you.”
“The Virgin Mary at Fatima was God’s last olive branch for peace in the world today. Is it any wonder that there is such an overlap between the generosity of Jesus and His Mother Mary? In fact, Jesus revealed to Sister Lucia in the 1930s that He wanted Mary’s Immaculate Heart to be honored alongside His, and hearts that love the same things share the same dispositions towards others. In fact, His request simply reiterated what Our Lady herself had already revealed on July 13, 1917: that God wants to establish devotion to her Immaculate Heart in the world.”
Retrieved August 31, 2018 from https://traditioninaction.org/religious/d013rp15Decades_Stretenovic.html