Material Choices

Do you have trouble choosing materials for your projects? I do.
I can easily draft up the plans whether I’m doing a sewing project or some woodworking or jewelry or even a painting. And while planning, I get an idea for what I wood, metal or fabrics I want to use.
Then I go to the store and see everything that’s available – all the possibilities I didn’t even think about – and I get stuck wandering the aisles for hours, rethinking my plans. “Gee, if I did it with this fabric, I could use that scrap I have a home as a pocket.” “What if I used a heavier guage copper, would I gain durability at the expense of flexibility?”
Or I realise that what I want doesn’t exist. A couple of weeks ago I drew up plans for a small wooden shrine. The proportions are great and the size is just what I want. But the boards I spec’d are non-standard sizes, so the shrine is not yet built.
Today I went to Okadaya to get three meters of lightweight indigo linen and maybe one other fabric. It took me two hours and I ended up with my three meters of blue, plus 2.5 meters of novelty print cotton, 2.5 meters of brown cotton gauze and two meters of cotton plaid/stripe. I will sew them all up into skirts and pants this weekend, but that’s not what I’d planned.
So when you go shopping for materials, do you have a firm idea, or do you change plans mid-stream?