When should the project end?

Once I finish a project, I move on. Many times, I have just one or two more things I wanted to do with the project, and sometimes I get back to it. Sometimes not.

A few examples: I still have that mammoth sitting on the shelf for my 54mm cavemen; I wanted to purchase (but haven't, yet?) the 40mm scale stagecoach model from Sash and Saber for use with my 40mm cowboys (which I haven't touched in a year and a half); I had intended to build a teahouse for my 42mm samurai to fight around- I drew up plans- just haven't built it.

I guess my plans are getting bigger than my table, and some stuff is falling off the sides. I end up wanting to do too much, and what I have on the table suffers from what I want to be on the table next.
I'm going to try to start applying the philosophy I use with art to that of my minis projects: When I look at a drawing or painting I've done and feel the notion that, "It's almost there, just one more line ought to finish it," I stop, and I don't draw that last line. Usually, that last line is the one that messes up a piece of art for me.

So I think I won't build that teahouse now, nor will I purchase that stagecoach. Though, the mammoth will eventually get finished- that one I've already committed enough resources and time to. It's a mental challenge to just know when to stop, but once I can get there, my lead mountain will stop growing- I doubt it will erode, but at least it won't grow.

Sometimes, you have to introduce a physical mechanic to help your mental challenge when you end a project: For my ghostbusters, I purchased a Chessex figure box, the one that holds 40 large figures. As of now, I have enough figures (not yet all painted), ghosts, and one diecast car in transit to fill that box. I think that will be a good stopping point. Now, there is no pressure to see what else I can add to my ghostbusters collection, because there is no more space in the figure box.

Though, there is that perfect-for-my-project 12" plastic Stay Puff Marshmallow man (piggy bank.) All I have to do is purchase it- no painting or building needed. But is that the last line?