I'd also rather use a bike frame for decades (come to think of it all mine are at least two decades old already, some getting on for five decades), which is why I avoid the use of aluminium altogether and stick with steel. Nothing wrong with hi-tensile either; it actually has some advantages such as not denting easily if a bike falls over because the walls are not drawn super-thin. For a pure utility bike, hi-tensile is an ideal frame material.
My Aluminium frame is at 11 years of daily commuting so far which is not too bad. Plenty of older ones in daily use.
I know some riders prefer unbutted tubing for better dent resistance. Reynolds 501 was a low cost plain tube a step up from Hi Ten and not so expensive. The biggest problem with hi ten steel is the low quality of build and alignment rather than any inherent fault.