The problem is. The phones are still being made with faster processors to keep up with demands of the more demanding software. As the features are upgraded etc. so, for now, for users who require those features anyway, phones are still on a 3 year cycle. For me. I am noticing my 5s is beginning to hiccup some. I haven't tried the newer wares available, but I am sure they are much faster and usable. Even for my lessor needs.
Consider MS and Apple back in the early days. A desktop will last way longer depending on ones needs. A gamer might still need to upgrade every year or two. While for a general Facebook user a desktop may be usable for 5-10 years.
Plus, I have dropped and drowned my phone many times. It's mobile unlike a desktop. It still works well enough. But, the innards need to be as capable as the indestructible case. Or what good is having a Liquidmetal indestructible case.
Furthermore. Phone manufacturers need to sell phones. They need new features and gimmicks to entice people to upgrade. Plus Apple likes pretty phones. Who knows. I just don't see a Liquidmetal case being all that important for now. There are other options. But, who knows. I wouldn't be completely surprised if Apple did make a Liquidmetal iPhone either. Just saying there are lots of option. Watch makes more sense to me tho.
Just my opinions and best of luck.