Jiyu Kumite, or free sparring, is excellent for developing speed, timing, and power. It can also be a lot of fun.
Unfortunately, there's a heightened risk of injury when free sparring. Crashed knuckles, sprains, strains, and even broken bones can sideline even the most well-conditioned athlete. Middle-aged and older adults are especially vulnerable and it takes longer for their injuries to heal. So, while you may benefit from rigorous kumite, an injury can reverse all your gains.
The question is how to perform jiyu kumite with greater safety. I'm not convinced that protective padding makes it safer. I've found that when students wear more protective material such as shin or foot pads, they can become reckless. While a foam helmet provides some protection (especially from a slip or fall) many designs interfere with peripheral vision and might make it more likely that a student will take a blow to the head.
I've come to believe that the attitude and intent of jiyu kumite makes the greatest difference in safety. Jiyu kumite in the dojo is not competition. It's training. Because it's training, both participants in a match have a responsibility for the safety of their partner. If one partner gains an advantage that might cause injury to the other, then he or she has the responsibility to hold back. At the same time, the disadvantaged partner must respect the attacker and the attack.
If my sparring partner leaves his head open, I may strike him lightly on the face to point out that mistake. Conversely, my partner must not take an unfair advantage of my restraint, to counterstrike unfairly. That's what we mean by "respect" in the context of jiyu kumite (because if I had pressed the attack with full force my partner would have no chance to counterstrike).
If we remember that free sparring in the dojo is not competition, but training, and show this kind of respect, then we reduce the chance of injury. This means we can practice free sparring more frequently and have more fun.