Was wondering what a typical duration of production for a conventional bush bean is. I know a lot of factors such as how well the plants are cared for and heat can play into it. Here in the Northeast US I've had a solid three weeks of beans out of a few different varieties and they all have pretty much stopped flowering at this point. They are well cared for and get between 1"-2" of water weekly however I think it may be time to pull them up and plant again. Is three weeks of beans good or is it advised to stick it out and let them remain although they've greatly slowed?
Once flowering has ceased, the plant is pretty much finished.
To prolong the (plants) harvest period, pick the pods when they are firm and crisp, but before the seed within them has developed (matured).
When you allow the seeds to mature within the pods, that really is the beginning of the end of the plant.
If you have the room (and wish to maximize your harvest season), it is recommended to plant several crops, 2 to 3 weeks apart, up until 8 weeks before your first average frost date.
I'm no bush bean expert, but I would say 3 to 4 weeks is a pretty good harvest period for those plants.
Bush beans were bred to make mechanical harvesting easier, so they have a shorter harvest period than pole beans. 2-3 weeks is typical, so your 3 weeks sounds good.
As Mike Perry mentioned, you can plant successive crops a couple of weeks apart -- this avoids the problem (if you consider it a problem) of having a huge amount of beans arrive at once.
Also, if you're looking for a longer harvest, have space, and don't mind building some supports, most pole bean varieties will produce over a longer season. (And in my opinion they taste better.)