I have a client that was complaining about how her hair is getting so dry & brittle.
I asked her how old her dryer was and she told me it had to be at least 8 years old, and it was super cheap. Her flat iron was pretty old as well. She was almost proud of how long they lasted her.
Now, I am here to tell you that "cheap" blow dryers only last about 2-4 years before the heating element goes a little wonky.
A professional dryer will last you about 5-7 years. BUT.... In order for them to last this long, you need to take care of them.
Remove all lint & debris from filter.
If it starts making funny noises or goes from hot to cold. You need to throw it away before they get worse. I have had blow dryers that literally spark fire out of them.
Your irons need to be clean as well.
Having melted or burnt product on your irons & then applying it to your hair is not a good idea. You don't want to melt burnt product into your hair.
If you smell a bad smell or see any cracks in the wires.
It is time to recycle & buy a new one.