[blackbeans]

My experience as long term employee of a big bicycle manufacturer is different.

Yes, aluminium can survive a long time. But in general steel has a better chance to survive. The category of city bikes are low cost bikes, and the frames are as well. They are not so over engineered as you think as it is a very competitive market. The first generation VanMoof frames for instance, were prone to breaking.

While it is possible for a aluminium frame to reach 30 years lifespan, in practice the lifespan is shorter. This is because steel is more forgiving, it can handle dents and scratches where aluminium is more prone to breaking. Also the frames are usually hand welded and this can too be a weak point as it is hard to perfectly weld aluminum. It doesn't mean you can't ride a 30 year old aluminium bike or that it will auto destruct. It does mean that the bike is unlikely to reach that age.

[aembleton]

Is aluminium more brittle then? My aluminium frame has plenty of dents and scratches and its about ten years old. I've another thats 25 years old but isn't ridden as often.

Do you know what the median lifespan is of an aluminium frame? I guess it depends on how often its crashed?