Most of those older $300-400 Android phones are ewaste for the most part after 3-5 years. Higher-end everything is more valuable and generally lasts longer. $50 work boots vs $400 work boots.
Modern $300-400 phones however I think will last 5 years easily in terms of performance depending on your needs.
The Xiaomi Mi Band 8 and Huawei Band 8 are rather nice watches that do essentially the same thing as the very expensive smart watches for about $40 and they last about 2 weeks
I've got some bad news for you...