Well, I've never had a bad parcel in a swap! I find the crafting to be the funnest thing, and then to get something in return is an added and exciting bonus. I'm sorry you've had a bad time with swaps.
I agree that having a wist is a really good way to be a helpful receiving partner.
Antidigger: I have pm'd you too but I wanted to say here as well - don't stop swapping! Going by time as a guideline seems like a fine thing to me.