Quitting slowly doesn't serve you well.
At work or in anything else you do, people will remember how you ended things. All in, then out is the responsible way to participate and to end that participation. Too often, we seduce ourselves into gradually backing off, in removing ourselves emotionally and organizationally, as if making ourselves unuseful for a while makes it easier for everyone.
Professionals bring their A game to work. Every time. (Rare sports analogy: this is how good hockey players skate. Full speed, then stop.)
Of course you will need to close things down, quit your job, move on someday. The responsible way to do that, though, is not to act things out while you agonize over a decision. Decide, give notice, make the transition work.
Dropbox fell into the gradual trap with the Mailbox app they published for the Mac. They didn't support it well for nearly a year, and the last iteration of it broke many of its features. It's as if they wanted people to quietly disappear so they would have an easier time shutting it down.
If you want people to believe your promises tomorrow, it helps if you kept them yesterday.