I'll just point out that the aircraft maintenance industry has extremely strict guidelines on component lifespan, with testing and replacement intervals specified, because aluminum DOES have a different metal fatigue profile than steel, titanium, etc.
i'm not saying every aluminum bike frame will crumble at the 10 year mark; I AM saying they were designed with a certain lifespan (as is every single manufactured item on the planet, whether people like it or not, because physics and entropy) and that the longer they are in use, the higher the chance of failure.
Please, everyone, go ahead and ride any bicycle you want for as long as you want. I am still going to inspect every aluminum frame that comes into my hands with extreme care. And I'm going to ride my own aluminum e-bike very happily for several years, though I do plan to sell it on eventually and upgrade to whatever the next evolution is.
Tangentially related: I acquired a 65 year old Elna Supermatic sewing machine yesterday. It is gorgeous inside, fully mechanical, incredibly well built, and once I replace the brushes and re-wire the motor, it will probably sew for another fifty years. But it weighs 20 pounds without its case, and when it was new, it cost a full month's wages for a middle class earner. (Retail price was ~$200 in 1956 - online inflation calculator estimates that at $1850 in 2018). Its user manual is 50 pages long and operating it takes a lot of practice. Modern sewing machines with the same features weigh less than half as much, are extremely easy to use, and cost under $200 in *today's* dollars. No, the new machines won't last 65 years, but they work well and are accessible. That does count for something. The world has changed immeasurably in the last few decades.