I’ve had mine from IKEA for years. I restain it every year or two. Still going and I leave it out uncovered over the winter because I’m lazy 😂 More on reddit.com

Teak is a conflict lumber and is banned from import in the US and the EU. Sales of teak support the military junta in Myanmar. More on reddit.com

You can reduce or remove the silvering from weathering on the table with oxalic acid. I make a saturated solution, where there are undissolved crystals in the bottle. Apply it as many times as necessary, letting it dry between applications. When you're happy, neutralize it with baking soda in water, rinse that off. I'm not so sure on the coffee table, the brown color tells me that there is something else going on there in addition. As far as prevention, understand that there is NO clear finish for wood that will withstand outdoor conditions. Not yet. And oils are useless. The best you can do is a good spar varnish with UV blockers, at least two coats. And even then it won't last two years unless you buy or make covers for when it is not in use. Hint: don't varnish just the top, do both sides equally, or the unvarnished underside will absorb humidity and cup. There was a similar query in today's post about a circular outdoor table with benches; skip forward and read it. More on reddit.com

I'd use a blend of boiled linseed oil and beeswax. Really stinky initially but smell won't last long outside. Gently heat 1 part beeswax until it just liquifies then add 3 parts oil (the cold oil will prob solidify the wax), warming until it liquifies again, allow to cool. Do it outside if you can as the volitiles in the oil smell a lot. The oil soaks in and the wax will stay on the surface to help protect it. More on reddit.com