I think I'd thread baste vs. pins for a couple of reasons. One - if you suck up all your pins on things that are just hanging around...you have no more pins unless you buy them. Two - if your climate tends to damp, depending on how long they will hang out without quilting there may be a chance of rust. Otherwise, I would think you could leave them basted for just about forever. I know others have mentioned creasing. A friend rolls her quilts (finished or not) into a ball for storage so they don't develop creases. Personally, I don't know that I'd worry about creases. I wash everything after it's completed anyhow and I think any creases would wash/dry out during that process. JMO.