custom jewelry:) and why do the best ideas always come at the last minute

I get it. Some minds are just at their best when last minute pessure is on. In school, I wrote my best essays the period before they were due. Won contests with them. It was unbelievable. Panic brought on clarity. Valentine's Day is over, so at least That pressure is gone, and hopefully this post will help out for later holidays, like Mothers Day(?)
Where I work, we don't send our jewelry out to be worked on. We have our own shop and we do it all there. The work we do is a mix of things we sell and things that people have been passed down for generations. When people call up to ask about repair work, they always want to know," How long does that take?" And the answer is this: It's not that the job Itself is time consuming, it's that 15 other people have dropped off things for us to do and they all want it done the same day as you.
Disappointing people is never fun, and I do my best to avoid it, But your best bet when considering custom work(unlike a general repair) is to plan ahead. Holidays like Mothers Day and Christmas are HUGE for custom jobs, and a lot of works goes into constructing a one of a kind piece of jewelry.
There are drawings, wax model after wax model, then you move on to casting and finishing, stone setting (if there are any)... The process can take weeks if not months depending on the job. If you want a necklace for your wife for Christmas, you shouldn't start the planning process on December 1st. Overestimate rather than under.
Every shop is different. There is no standard of things to be kept in Stock at all times that applies to goldsmiths around the world. It could be that what you want requires a special part that takes 3 weeks to get, or the stone you want has to be color matched, or cut specifically for your job. While I would love having everything at my fingertips, it simply can't be. Money is lost when things are kept in Stock, but not used, So items that are needed frequently are what's available. I say again, plan ahead!

Lastly, it's best to discuss these kinds of deals in person, rather than over the phone. Set up a consultation with your jeweler where you can go in and talk about your ideas, or ask any questions to get the ball rolling. Don't call them up and expect a quote or 30 minutes of their time over the phone. Remember that other people have gone ahead of you and are expecting their jobs to be completed on time, and that won't happen if they're having an impromptu phone conversation.