I think it depends on how much you are willing to maintain it and if you are flexible on the types of materials you use. Where you live will have a significant impact as well, if you live near the sea up north then you are going to have a harder time than if you live inland in the south.

BLO works but you will have to maintain it regularly and how regularly depends on the weather.

You can use specific wood types that work well outside; pressure treated timber starts off looking a blue/green colour but fades to a silver and won't need looking after for a long time. Teak is the classic option for outdoor furniture as it's naturally resistant to pests and erosion, it's an exotic hard wood though so not the most sustainable. White oak is resistant to rot as well but isn't easily available. . Any of these with an annual coat of BLO will probably keep them looking new, if you don't mind them becoming more rustic then you can leave it for longer.