When to say "f@*k it" and give up on a project

As I keep mentioning, I have quite a few cigar boxes and I finally decided I want to turn them into dollhouse type rooms.  I've been in love with dollhouses for as long as I can remember and decorating my home is quite possibly my favorite thing to do so this seemed like the perfect fit, right? WRONG! I've been working on my first room for a few weeks now and at this point I'm so frustrated that the idea of finishing this project  (or starting another one when I'm finished) is starting to seem highly unlikely.

It started out going great.  I picked some fun patterned papers and set to work "wallpapering" the inside of my box.  Once that was done I searched through my stash and found the perfect buttons and embellishments to make a mini gallery wall.

So far, so good!

Obviously, the next logical step is to "furnish" the room.  This is where the trouble started.  Let me try and put this nicely:

Making dollhouse furniture is a mother f@*ker!

At this point, I've spent at least 15 hours trying to make a mini upholstered chair and unfortunately, all I have so far is a plain cardboard chair with cardboard cushions.

 

The problem is with the upholstery part.  I've spent countless hours trying to figure out the best way to cover it and I'm stuck. I know I could always buy pre-made dollhouse furniture, but that just feels like cheating.

So my question is, how long is too long to spend trying and failing at a project? I hate to give up on things, especially when I've already spent this much time on it, but I'm unbelievably frustrated. 

Help!