artery life expectancy

What is meant by one artery lasting longer then the other in a bypass?  Using the artery in the leg doesn't last as long as using an artery from the chest.  What is expected at the end of this artery life expectancy?  Does the artery dissolve, plug up easily, detach, ...??... and am I to look forward to having the original artery pathway to be used again?

[ed34]

There is a difference between veins and arteries. There isnt an artery you can lose in your leg for a bypass, but the body can cope with losing a few veins. Arteries are much stronger than veins and veins have tiny flaps in them which act as one way valves. When these break down, the vein wall weakens making it swell and varicose.
So, due to their superior quality and strength, arteries are the favoured vessels for a bypass. They can use one of a pair from the left side of the chest and one from a pair on the right side of the chest. It is common for an Artery + a vein to be used in a bypass.
Veins do not last as long as arteries but there is nothing else to use when there are only two arteries you can spare in the area.
It greatly varies from person to person how long the veins last. Mine lasted 3 months, whereas some last up to 20 years or more.