Can I use softwood for garden furniture?

I also have access to lots of wood. I made some benches and table from it and stained for better visual effect, as well as garden beds from untreated wood of all kind. It already lasted two years and it looks like a couple more years will be OK. Since the wood is available and doesn't cost anything - I see no reason to worry how long it will last, just make a new item in 5 years.

I used treated southern pine for a built in bench ( 20 ft long) on a deck of the same material . The bench if fine after 20 years but the deck has had a couple bad spots because it it wet longer than the bench. So soft wood can work fine or not;depending on the wood,treatment ,and how much time it is wet. ( Southern pine -US- , is one of the hardest softwoods.). Stain /water repellent , will work better than paint for exposed wood.