The best people you can spar with are the higher grades....because they know what they're doing. It's the other lower grades you have to be more aware of, and more on your guard. Because they're the ones who don't know what they're doing, so you may well end up getting kicked in the nuts. PS.....ALWAYS wear a groin protector. Not just for sparring.....wear it at all times so it becomes a natural thing.
5 years to reach 1st Dan, 2 years more for 2nd Dan, 4 years more for 3rd Dan, 5 years more for 4th Dan.......and since then I've held my 4th Dan for 20 years. I'm getting my moneys worth out of this one!