It is a bit of an old wives tale about all aluminum frames having a short lifespan.
It started with some of the first aluminum frames, which had lightweight, small diameter tubes. In some cases, the tubes would flex too much and the metal would fatigue, leading to cracks and/or breakage. In some bonded aluminum lug frames, poor adhesives would fail and tubes would come unbonded from lugs.
Modern adhesives have solved the bonding issue, and maufacturers have solved the fatigue issue with larger tube diameters which stiffen the frame substantially (which in turn led to Aluminum’s reputation for harshness).