I think this is very hard to pin down.
Speaking for myself I consider myself to be very experienced both at the field and husbandry level. I have worked with three different zoos as a volenteer and was the "reptile specialist" for an animal shelter at one time. I started working with snakes heavily via a family friend at 10 and was handling hots by the age of 12. I currently have a very diverse collection of small to large snakes and have had to deal with enough typical problems to know how to deal with them. I have preformed removals for more then a decade now, etc.
Does any of that make me an expert? Nope not in the least!
I would also tell you 99% of my experience is with snakes, talk lizards and get past leppard geckos, iggys and anoles and you are beyound my knowledge.
There is also specialization to consider.
Such as would I put my corn snake knowledge to the test against Don Sonderberg, Kathy Love or Rich Z? Not in the least but I would bet I know more then the three combined about Lamprophis.
I hesitate to call anyone not fully engauged with snakes as full time employment an "expert". To me an expert is a very specialized individual.
I consider myself and many of the people on this forum "advanced" or "highly experienced" keepers but don't know how many experts I really know. The three people I mentioned with corns I would certainly call experts in that niche but are they experts on all snakes? I don't think they would tell you that.
Beginner seems much easier to pin down. I guess expert is a very subjective thing. Many of us would say we are not experts but I would guess many people that have less experience might consider us to be.
I think to much is made of "experience" with snakes over all. Most just are not that hard to keep happy. Also consider a person may be a great keeper and breeder but not really know much about their snakes scientificly. Just what temps to keep them at, what to feed them and what patterns to create for breeding. Another person might know Genus, Phylum and Species front to back but have no hands on experience. Another may have field herped for 25 years but never preformed captive care. To me each might be an expert in an area but not over all.
I think two things are misunderstood in forums online today
1. That simple time with animals makes one "experienced" or that having a lot of animals makes one an "expert", neither is the case.
2. That a person with a few thousand posts in forums must be some sort of expert. (this is by no means confined to herp forums it is common in like every niche).
In regard to these two issues, I think it is more about either specializing in some area during that time or in that quantity or being very broad in species and still pulling it all off with thriving animals as far as "experience" making you very capable in regard to husbandry.
As for being any kind of expert because of a bunch of forum posts. I just think that is silly. I do not see much of that thought train here though at BP.net which is great! There are some others though (some of you know what I am talking about) where anyone with a 500 or so posts is regarded as some type of snake yoda,.
Anyway to me in the amature world where most of us live I don't think many are truly experts, just a bunch of people that love animals and try to learn a bit more about them every day.
In short to me an expert is a "master" and mastering anything as complex as snakes and other reptiles seems quite unlikely,