To answer your first question, I actually don't think it's a big deal. It may become important if you end up having a ton of models running in production that

To answer your first question, I actually don't think it's a big deal. It may become important if you end up having a ton of models running in production that need to be maintained and further developed, but in general for new applications I would say that substantially less than 5% of your time would (should!) be spent actually writing any code.