There are few or no Aluminium bicycle frames.. Ali is way to soft. They are mostly Duralamin (cheaper end) up to exotic alloys that may have magnesium thrown in. Same with airplane frames it is always more exotic alloys. It is a little misleading that manufacturers also say Aluminium. Really real Aluminium is not used for much, it is a very soft material. What is used in everyday life is almost always alloys of aluminium.

Assuming a rider is not over weight, and you are on good roads, an reasonable quality ali alloy framed bike can last a life time, but welds in particular can fatigue and fracture, especially in areas of extreme cold.. and rough roads.

Practically for most riders I doubt there is ever an issue... but for sure the manufacturers of Carbon frames will gladly point out the issues with ali alloy frames, forgetting maybe that 5 years ago they were marketing their own ali alloy frames as the best thing since sliced bread.