Hello there. I usually recommend my students to try the nail technique on the 4th year of playing, age being irrelevant. It usually takes 3 years for them to stabilize their technique enough and develop hearing well enough to know what kind of sound they want. Some of the kids get there faster, some never. Myself, I started playing with nails after 1.5 years. It was a bit too early, and I struggled for a long time, blaming my nails when I simply didn't have proper right hand technique yet. In other words, too many variables too soon can be confusing. Just my two cents.