There are all the mnemonic devices, too. I learned Every Good Boy Deserves Fudge for the treble clef lines. FACE for the spaces. My kids piano teacher seems to have a different one for the lines. You can make up your own, if you like. Plus there were ones for the bass clef, too.
My son started when he was four. He’s now eight, and it’s finally starting to come more easily for him. He uses all the tricks he can, though. I don’t remember how long it took me. I do remember my trumpet teacher asking me to name the note I was playing. I knew the fingering, but not the name of the note. But one day, it kicked in, and now I can’t imagine not knowing them.
Piano is more difficult than single voiced instruments, because you do have to learn the F clef and the G clef. I still don’t know the notes of the F clef very well, and I’ve been helping both my kids with piano for 8 years now.
My daughter can now go through song after song, and she has a good voice, too. My son likes it when we jam together. Not too long, and we’ll be able to have a pretty hot combo. Although, we better not be doing that hiphop they like so much. Then again. It’s music. It’s all good.