[joshdotsmith]

I think the answer is "Yes."

By that I mean that I think people often mean both. Some projects are obviously hackathon-like projects that were done in (something close to) a single weekend.

Others probably took on the order of 4 days to a few weeks cobbled together over weekends. I worked on http://lifestyle.io/ for probably about 5 days total before launching it, and I've given it additional love since.

I wouldn't get hung up on what you can get done in a weekend anyway. Focus on creating real value with what you do if you're intending to profit. (Hint: many of these weekend projects forget that part entirely!) If you just want to have fun, then you definitely don't need to worry about timescales.