Alright, let me try this calculation.
*NOTE: We are using the diameter of the roller and not the bearing, which is less. But you will see how well they have worked in a year. Math folks, please correct any errors you see!
5,280 feet in a mile
63,360 inches in a mile
1 3/4 = 1.75 roller diameter
1.75 * 3.14 = 5.495
63,360 divided by 5.495 = 11530.48
So, 11,530 revolutions in one mile
1,000,000 times 11,530 = 11,530,000,000
Read outright it is: eleven billion, five hundred thirty million total revolutions.
But wait, (scratching head) there are two bearings, so that doubles the total per bearing to 23,060,000,000.
Without any bearing failures!