With our recent extension we also added a LOT of merbau decking, which has sat through Winter and now seems to have lost most of the tannin. Put the first coat of oil on yesterday in fact and it looks great. I reallyl ike the Sceney's Old Fashioned oil - cheap, rolled on easily and only slightly darkened the timber. Noticed today that the timber has lightened up a bit . The Sceney's stuff is basically the old turps and linseed mix, with some added ingerdients. Used it on the oregon verandah posts and once it dries it leaves a nice hard satin finish. It didn't change the colour of the oregon, just enhanced it.
Have been using Sceney's for years on outside timbers and I reckon it is a great product.
The decking will get another coat in a few days, then again in November, and then it should be right for about 2 years before needing another coat.