There's a lot of talk of the Pacers being over their projected design life. But what was the projected design life for other stock? For example, the first batch of 317s (the "/1"s in service with FCC and /5, /7 and /8 with NXEA- all originally /1) are now 30 years old (introduced 81/82). The 455s are 30 next year (with some trailer cars being older, and much of the traction equipment even older). The 313s are 35 years old. Some Mark 3 carriages are as old as 36. The 319s, which are supposed to be cascaded once Thameslink is done with them, have their 25th birthday next year. Even the "modern" Networkers are 20 this year. How long can all these units go on? At what point will the chassis and bodies become untenable?