I am inclined to think we are four-dimensional (or, more precisely, (n+1)-dimensional, where n is whatever number of dimensions space turns out to have) beings, but that we do not have temporal parts. So what do I say about apparently monadic properties that one can change in respect of, like being red? My preference is to say that these properties are, in fact, non-monadic. For instance, "I am beige" (or whatever color term correctly indicates the current typical shade of my skin) expresses the fact that I beigely occupy the present, where the present is a spacelike hypersurface.
Presentists can say, more simply, that "I am beige" expresses my being beige simpliciter. So it seems that on theoretical simplicity grounds, presentists win out. But I think this is mistaken. For whereas presentists need to posit two properties—a monadic being beige and a binary beigely occupying—eternalists of my sort need only posit a single binary property of beigely occupying. (Of course, the presentist could analyze her being beige in terms of beigely occupying the present, but then the presentist loses the advantages of the theory.)
Here is a reason why the presentist needs a binary beigely occupying. I am beige on my left half. (I am also beige on my right half, but nevermind that.) Given a relational beigely occupying, I can let L be the region of spacetime occupied by my present left half, and analyze "I am beige on my left half" as "I beigely occupy L." But this uses the relation of beige occupation.
I do not think this can be done with mere monadic beigeness. The best way I know of rendering "I am beige on my left half" in terms of monadic beigeness is something like "My left half is beige." But there is no such object as my left half. Cutting me in half is not cutting nature at its seams, and if there are such things as parts at all, they are obtained by cutting nature at its seams. But it's worse than that. Suppose there were such an object as my left half. It wouldn't be beige! For one of that object's surfaces—the one where the object meets my right half—would be mainly bloody red.
One might try to talk of the left half of my surface being beige. But a surface has two sides, which can have different colors, and so we would still need a non-monadic property: being beige on the outside/inside. Or at least a pair of monadic properties. But not just the plain monadic being white. Besides, I don't think we have surfaces. Those would be weird things in the case of beings whose material components are made up of particles or that have blurred wavefunctions.
So, the presentist also needs beige occupation in addition to beigeness. But isn't it simpler to just analyze the latter in terms of the former?