My mother-in-law and I have been chatting for awhile about making a new leather handbag that would let her carry her entire kit (laptop, books, etc) all in one thing. We went through a few drafts before settling on the details and the final measurements (5.5" deep x 13" tall x 17" wide). I budgeted 60 hours (about a week) for the production which seemed pretty conservative at the start. Thanks to a timing app I've been using this year I can look back and see that it took about 140 hours (in about two weeks). So clearly I could be better at forecasting ETDs for big projects.
The shell of the purse, including feet and handles, was made from tan stone oiled leather that's got just the right mix of flexibility and rigidity. The interior is a drop in lining (to allow for a pocket) made of poly-cotton and a deerskin edging that interfaces between the lining and shell. Wrapping around the top is a carved strip with a sheridan-ish design featuring daffodils.
All that sheridan carving, especially with all that bargrounding, took about 3 days to finish. Fortunately I'd already assembled some of the shell before I started the long strap that would go on the front of the bag. All the measurements had been checked several times in the drafts but geometries have a fun way of warping with complex projects. I realized the 27" strap I'd planned was going to be at least 3" short. I added a couple inches for "wiggle room" and redrew the design for a 32" strap.