Mine lasted 2 years.....
Make sure you only use these type of seats on completely flat ground, unfortunately all the joints in mine came apart due to a slight slope of the garden
Not particularly lightweight TBH (although by no means heavy!) BUT you NEED to treat this as soon as you build it to get any sort of longevity. Had ours for about 4 years now, been out in the weather all that time and still in good condition. Reason being I gave it 2 coats of quality yacht varnish a few days after i built it (in that time before the varnish was applied we had a downpour and the rain just soaked right in immediatley which is not what you want!). After the yacht varnish application rainwater just rolls off.
looks lightweight !