I trained this is the Chinese system when I was in my 20's extensively, and less with each decade. I regret the loss of some of the flexibility, so I might work back toward greater, because it's really optimal if someone, for instance, gets your leg. But it's exponentially harder to get my leg than it was when I was in my 20's.
- Joints can be a problem—you've just got to relax.
- Keep strengthening the muscles around the joints to this end.
I learned floor stretching on hard linoleum and practiced on hardwood, concrete, and stone. (Today I'll take a carpet if I can gt it, not too soft or deep, but I like to remind myself on flagstone;)
½ hour is good, especially for class, where you want max time for training. When I used to do full warmup in my 30's and 40's on my own that could stretch to an hour or more. They say for really doing the split, "watch tv" i.e. do just that as long as you are comfortable.
The main thing is don't over stress the muscle by pushing too far, too fast. It's a slow process of isometric strengthening, and gentle gentle gentle bouncing within your current range of flexibility can be helpful. Do not do not do not use bounding to try and increase flexibility—you will tear something.
I use front and side splits to gently strengthen my knuckles and wrists for punching. Since I rarely have gone all the way down, it's always an extended upper body isometric too, because I support my weight with my fists.
My advice to women would be different than my advice for men, because women's hip structure allow them to really "sit" in the floor with total root, making techniques that utilize it.
In a weapon like jian, this could be determinative (think instant level change below an attack with jian thrust up unto the unguarded guts. People charge people with straight swords, which is always a poor strategy against a short thrusting weapon.)
A male teacher who worked to go all the way down reports hip problems later in life, and is not recommending men be extreme, and I'm adopting that advice, though I still might cheat it if I get back down for one or two moves in a performance context.
In a sword sparring context, as a male, I wouldn't use that split because you need that root to "guarantee" the thrust. I don't know that I could recommend it for women either in sword sparring because the attacker is probably going to damage themselves, even with the blunt sword and protective gear.