Breast thermo pad

Hi mummies, ftm here and preparing baby stuff. Do I need 1 set of breast thermo or best to standby 2 sets. 1 specifically for cold treatment, put in freezer(cold) & 1 for microwave(heat). I read that if we get painful engorgement, we can use cold therapy first to relieve the pain then heat therapy. But if i have 1 set, scared i dont have enough time to freeze it when i need the cold therapy. So thought of keeping 1 set just in freezer, another one for microwave. What do mummies think? Is it necessary ? I dont have experience so abit noob here. Usually will both boob feel engorged at the same time or usually only one at a time ? #pleasehelp #FTM