About 15 years for me. I wouldn't consider myself advanced... I've probably run into more problems than someone whose only had their tank up a few years though Lol. So that's just experience ... not skill. I've also gotten slightly better at seeing the reefers who really know their stuff.
Regardless , I'm Still having a blast and one day I will get a few of those danged sticks to grow in my tank.
If memory serves, I've been in the hobby around 33 years. Listen and learn from others; share your own experiences. It's been amazing to see what has come about in the hobby over the last decade. In the beginning (for me), Martin Moe's first two books (The Marine Aquarium Handbook and more importantly, The Marine Aquarium Reference) were both full of crucial information. I wore the Reference book out and bought the next edition. lol Other books and articles from Calfo and Sprung were essential as well. Online forums have advanced the hobby for me to a whole new level. The ease at which we can search and share information, ask questions and get opinions from those who have been there before is just amazing. Thanks Reef2Reef, WetWebMedia, ReefCentral, BRS and others who facilitate greater knowledge.
I'm going on 50 years keeping inverts (and that was before the term "reefing" entered the aquarium keeping hobby).
My "sound advice" is: "There are Many Paths up the Mountain". There are many, many, many successful methodologies for keeping a reef tank. So (1), don't believe everything you read - there's a lot of reefing myth on the Internet, and (2), do your homework and seek the best path for your own skill level and finances!
I wouldn't consider myself an Advanced reefer with 20 years experience. I set the bar low and keep softies and LPS, most things a beginner should be able to do pretty easily with WC, good light, good rock, maybe some kalk dosing. Also don't overstock your tank with fish.