my rule of thumb was if it takes 4 hours to develop, I'll always said 3 days, as then You account for some unknown, testing, building / deploying, maybe some re

my rule of thumb was if it takes 4 hours to develop, I'll always said 3 days, as then You account for some unknown, testing, building / deploying, maybe some refactor after review, etc esoecially as it was for a product that will run for 10-20 years, with changes allowed like once per year. In 60-70% I'd finish in 1-2 days, but in those 30% it's always good to have extra day available for additional development or debugging or anything else or You can always tell You're finished ahead of scedule and feel really good about Yourself! :D