There are a lot of question so I will settle on the one in the title. How many years will an current aluminum frame last of a touring bike? Depends: - Don't know what aluminum frame Construction is a larger factor than material - Don't know the use Use is a larger factor than material - Don't know how you are going to care for the bike Care/maintenance is larger factor than material Aluminum has not changed in the 10 years All we know is your last aluminum, high quality, strong frame bike lasted about 10 years The best guess is your next aluminum, high quality, strong frame will also last 10 years Really that is the best guess That is as vague as how long will a current pair of sneakers last me? And the best guess for how long my next pair of sneakers will last is how long did my last pair last. Aluminum fatigues and steel does not fatigue. As stated in a comment steel does fatigue - well not always. Mild steel will not normally admit fatigue crack growth if the applied stresses are below about 10% of the strength of the material. Good steel bikes are designed to stay under that 10%. Materials, such as aluminium alloys, do not have any such fatigue limit. If a cyclic load is applied, aluminium alloys will always fatigue. For the same strength a steel bike is typically going to be heavier than aluminum. But you get a bike that is much much less susceptible to fatigue. With steel you also get a bike that will take a ding (dent) and not compromise structural strength to the extent of aluminum. Not exactly the same thing but at the molecular level they are related. If you are discounting steel because it will rust then you are not caring for the bike properly. A properly maintained and stored steel bike should not rust. And for sure it should not rust out in your life time. You stated bikes from you fathers era lasted 40-50 years - pretty sure they were steel bikes. If you want fatigue free and rust free then get titanium.