[reset my expectations] reasonable expectations for shipping times on mail order car parts

what does everybody think is reasonable for shipping times on mail order parts?  I have started to assemble some upgrade parts for dunceCar and have found a variety of shipping times some of these have exceeded my expectations to others that were well below my expectations; here are some examples:

1 manufacturer I ordered a part from them, I got an email when the order was confirmed, an email when the part shipped (2 days later) and an email when it was shown as delivered (4 days from order date) this is well above my expectations.

1 manufacturer agreed to sell me components of a kit to upgrade my current set of parts to a higher spec and when I placed the order I got an email that custom orders take 2-3 weeks to build and the parts were shipped just over 2 weeks after I placed the order.  They set expectations and met the fastest end of them.

1 manufacturer the order sat on the website as "processing" for 1 week, i emailed them twice before they responded that the part would ship the next business day, to date I have no follow up that confirms if it actually shipped.

by far however, the worst is 1 manufacturer that sold me a set of brackets and after placing the order and not hearing from them for 2 weeks I followed up and was told that they didn't realize they were out of raw stock to make the part and would pick up more the following Monday, to date more than a week after that i have no indication if the part shipped, etc.  At this point I have been waiting for the part for nearly 3 weeks.

I fully understand that in the world of custom car parts and JIT delivery it is impossible to inventory everything and in several cases it may take 2-3 weeks before the job gets to production in the queue, so my question is what do you consider acceptable?  also when its taking longer than expected what level of communication is appropriate?  

Generally, my expectation is that if I place an order for something that is not explicitly identified as being out of stock or made to order, it will be in the shipper's hands by the close of the next business day.  There is no reason that it should take a business more than a day to grab something off a shelf in a warehouse, drop it in a box, slap a label on it, and hand it off.  From there, it should take the carrier no more than 5 business days to land it on my doorstep.

There can certainly be extraordinary circumstances that would change that timeline, especially weather, but generally-speaking, from order submission to on my porch should be no more than 7 business days.

I have no problem with something taking longer than that to get to me as long as that's called out in the ordering process.  If it's coming from another country, that'll take some time, so let me know.  If you have to make it for me, that'll take some time, so let me know.  If your warehouse is empty and you're waiting on your supplier, that'll take some time and you will have gotten an estimate from your supplier, so let me know that. 

Stuff happens sometimes so if something happens and the widget is going to take longer than originally anticipated, just tell me.  Give me an estimate of when you expect to be able to ship it and give me an option to cancel the order and give me an option to expedite the shipping.