(04 Apr 2019, 5:29 pm)Malarkey wrote But back in the days of United and Northumbria the vehicles they had back then the likes of the National's and ECW Olympians were built to last though. 

Look at some the vehicles up here in the North East which have since been preserved, most of them despite their age are in way better nick than the vast majority of vehicles in the current fleet at Arriva.

Regardless of the differences in build quality to then yonder and now, operators will plan to depreciate their assets over a certain number of years.

Keeping them any longer, either due to a financial need or because they didn't "need" to replace them, is just a bonus.