Are extendable dining tables sturdy enough for everyday use?

It depends on the mechanism. Reviewers on r/furniture and r/kitchenremodel repeatedly flag butterfly-leaf and slide mechanisms as the failure point, with some pricier brand-name tables noted for jamming over time. Tables with simple drop-in leaves and reinforced aprons tend to draw fewer complaints. Look for verified-purchase reviewers who report using the extension repeatedly, not just at unboxing.