If your design is questioned, do you have the calculations to support it readily at hand, in a complete and presentable format? Do you ever shuffle through stacks of notes to double check a pipe or control valve size?
When an engineer working on a project I was managing left the company and we looked for information in his files, the only design calculations recognizable as such were those produced by various vendors' equipment sizing software programs. We needed design data to respond to a question from the client regarding system sizing and it was embarrassing, to say the least, that we could not immediately provide an answer.