I've thought the same thing not all that long ago, but, a SW tank is still a SW tank, and while you can get away with a bit more neglect on a fish tank, you still need to take care of it. And with the anemones and mantis, you won't really save anything. It just seems that the minor reduction in effort wouldn't justify it, unless you have lost interest in corals, and have gotten more interested in the fish.
To me, the question would be more along the lines of 'tank or nothing'. Unfortunately, I can't answer that question for you. The key to my enjoyment in this hobby is sharing it with other people. The more I can do that, the more I enjoy it. Before I found MARS and even RC, I nearly quit because of the young kids, crazy work schedule, and the hobby had become a chore rather than a hobby.
I obviously hope you stay, but can certainly understand your 'pondering'.