Ive had my dogs nail clippers for 1.5 years. Never sharpened or anything. Cut nails once a week or once every 2 weeks. When should I replace the clippers? Can I sharpen them or do u just replace them? I dont want to make it uncomfortable for him. He doesnt really care when I cut his nails so it must not be bothering him much right now. Just wondering how to know when they are getting dull or need sharpening/replace.