It worked for me. I started at 15' and I constantly practice at that number on up to30' or so. I found my long putting improved, because I found I didn't need to jump putt until approx 40' out. All said, putting has always been my priority. Since I don't throw for much distance. So I do spend quite a bit of time putting in my spare time.Some of the new players at our course call me "The putting guy" Since that's all they see me doing.
I started really close and worked my way back. I rarely miss anything outside of 20 feet anymore. I put with a completely different stance outside of 30 feet, so it had no real affect of my long putting. The repetition and the dedication is what really makes the difference.