Some numbers are spiritually significant as they contain symbolic inference and reference. The New Testament has 14 years as being a long time like what Paul mentioned in Galatians that he was not seen by Christians for 14 years before reappearing again (Gal 2:1). Then there are these 3 epochs of 14 generations spelt out by the Gospel of Matthew. I suppose 14 stands for a long time because it is double that of 7. Seven years is a complete cycle of years or a cycle where Israelites work for 6 years and then on the 7th year the land is laid fallow for a year before sowing is resumed in the 8th year. God promises to bless his people three-fold on the 6th year so that they don't have to worry about their needs on the 7th year and also the 8th year until harvest time. Then 70 years is the span of a man's life on earth (Psalm 90).
70 years is 10x7, a long life as most people during ancient times lived to mid-50s and if they are strong, 70 or even 80, so says the Psalmist. As far as a person reaches 70, he enters into old age. Even the Government's SOP for religious services is to bar those above 70 years old as they are considered more vulnerable to the infectious disease. As for me, I don't have time to waste. In 14 years, I will be turning 70. Even if 14 years is seen as a long time, but time is ticking by the minute, a day passes in the blink of the eye, a year is gone like yesterday. What are you going to do if you have only 14 years to serve God? How are you going to spend your money? How much are you going to invest in the expansion of God's kingdom? Would you dedicate these remaining years while you are still strong to serve the Lord?