I'm a total newbie, putting together my first housing with ports, a nauticam for sony a6500. the macro port option I chose for my 90mm required an extension ring. The extension ring addition is sealed by the port's original o-ring, a clever design. But, I'm just wondering how often the port o-ring might need inspection? Not a big deal to remove the extension ring, though it does take some time, with 16 screws to remove and replace. So I don't want to do this more than necessary but don't want to miss important maintenance either as i could see that o-ring easily fading to out-of-sight, out-of-mind.