I made a brave move today and brought down some of the gifts I had wrapped a few weeks ago to put under the tree. Briefly I considered waiting to put them under the tree while Silas was napping, but figured he would wake up and think they were all there waiting for him to rip them open. So, instead I carried them downstairs and he helped me put them under the tree and I told him who each gift was for (without mentioning his to avoid any confusion).
So far they have lasted half the afternoon. Once they were under the tree he didn't touch them again.
Only 17 more days until he can rip some open!