Pretty much finish is going to need repair/restore work after a while. But the best true marine spar varnishes (such as Epifanes) are going to last longer and do much better. Use something (anything) from a box store and it may make it 6 months, most of them have urethane resins which just don’t do well outdoors. If you can still buy oil based paints a good choice that would be long lasting, quite a but cheaper, and a little easier to apply would be an untinted paint base. The exterior oil base made for dark colors (usually #4, but ask) will dry clear, have the UV and good weather resistance. Some of the acrylic outdoor paint base (again, the ones for dark colors) also dry clear. By clear I mean the oils will like all the world like an oil based varnish…an amber tone. the acrylics (waterbornes) will be water clear, at least the 2 I’ve seen: Olympic Premium High Gloss enamel, and SW A-100 exterior. If any of this may be of interest, here’s more info.
"I long for the day when coke was a cola and a joint was a bad place to be" Merle Haggartd