I don't think Russell taught that 1874 would be the end, but that it was when Christ ascended to the throne (ie, his 'presence' instead of his 'coming'). This was not an original idea- the Millerites had dealt with the disappointment of failed end-times predictions in 1843 and 1844 by making the same claim, that they had 'expected the wrong thing at the right time.' But he did make clear that he expected 1914 to be the end of Armageddon, not the beginning of the end times.
Rutherford predicted the end in -if I am not mistaken- 1918, 1920, 1925, and 1941. The WTS hinted strongly at a possible end in the early 50s, and seemed to have learned their lesson until Franz's end-of-world itch got so bad that he could not help but scratch it, and thus 1975 became the next expected date of the end. From then on, they have preferred to tell us, over and over, that the end is closer than we expect. Or really really close. Or super duper close. And so on.