Indeed, free-sparring is important. (Use eye protection!) It's much harder than it looks.
It's worth bearing in mind that most street weapons are not knives as we think of them but box cutters (little stabbing ability, hard to disarm unless you use a lock like kotegaeshi that really opens up the hand), sharpened screwdrivers (stabbing weapons that you can do a forearm strip on very safely), or some such. A friend who is an LEO was asked how many times, in the past few years, he had taken a knife off of someone being arrested, and he answered that he had taken two knives--both from the same suspect. How many box cutters, he was asked; the answer, maybe 40 (I don't recall exactly what number he gave). Similarly for shanks, like the sharpened screwdriver--about 40, say.
So, the actual weapon one faces may make some defenses easier or harder.