Great question. For these park benches, the frame typically carries a lifetime warranty, but it is not a full lifetime warranty on the whole bench. The metal frame—usually powder-coated steel, aluminum, or cast iron—is covered against structural failure, rust-through, and manufacturing defects for the life of the product. That means if the frame cracks, welds fail, or rusts through under normal outdoor use, the manufacturer will repair or replace it.
The seat slats, backrest slats, hardware, and finish are different. Those parts usually fall under a limited warranty, often one to five years depending on the material and brand. Wood slats may have shorter coverage because they are considered a natural wear item, while recycled plastic or coated metal slats may be covered longer.
So to answer directly: yes, the frame has a lifetime warranty on most quality commercial park benches, but the rest of the bench is only covered by a limited warranty. I would still check the specific product label or manufacturer’s spec sheet, because “lifetime” can mean the expected product lifetime rather than your lifetime.