Are mid-range phones (Poco, Tecno, Realme) durable enough for multi-year use?

I'm testing the "buy it for life" philosophy with mid-range phones. Currently using Poco F7 and Tecno Camon Premier 20 5G—both solid so far, but will they last 3-4 years like flagships supposedly do? Has anyone successfully used budget/mid-range phones long-term without degradation? Or is the initial savings negated by shorter lifespan? Curious about real-world durability experiences.