Caminho portugues central way from Lisbon

You can get stamps whenever and whenever you like. If you want to "walk every step" you could go back, but if it's not important to you don't worry about it. The only requirement is if you want a Compostela you must walk every step of the final 100 km into Santiago, and on those days you must have two stamps per day in your credential. Most people get a stamp where they sleep then another one where they have lunch or perhaps from a church along the way.
After you finish your Camino you may treasure your credential and the stamps inside that tell the story of your camino as many pilgrims before you have done.