Honestly, if hindi sira at malinis pa, okay lang gamitin ulit, I have a few mum friends na ginagamit pa rin ang old sterilizers nila for their younger kids, walang problema! Just make sure to descale it well (vinegar works great) at check kung gumagana pa yung heating element properly, dahil yan ang importante para talagang effective ang sterilization. Since it's been sitting for 4 years though, I'd suggest having it checked or asking Philips directly kung safe pa if makakamura ka pa ng replacement ngayon, better safe than sorry with baby stuff, no?