I switched to Mac OS for work about 3 months or so ago and I have been extremely pleased with it. Definitely my favorite OS to work on and I've just discovered this Stationery pad feature, which when enabled, allows you to create a reusable template that will force you to save the file as a different name, eliminating the need for using Save As.
I run a business selling stuff online and everything I sell goes on an order form that the customer has to sign. Sometimes I accidentally save the master file when I mean to use Save As, which means that the next time I go to use the master file, I have to sit there and backspace, which is quite annoying.
Recently I switched to using PDF Expert instead of Preview for editing PDFs and I realized that every time I would try to Save As, it would overwrite the master file anyway (that was annoying to deal with), but I've realized this function exists within Mac OS and immediately set 3 different files I use often (2 order forms and my quote template) to be stationery pads.
Fun fact: stationary and stationery are different words, stationary means staying in place, stationery typically refers to office supplies like envelopes and paper. Apple chose "stationery" because it's supposed to be like tearing off a fresh piece of paper from a paper pad.
Edit - Not sure how many of you guys use Word, but this doesn't work for Word files, you need to use the Word template file format which is .dotx instead of .docx.