There is no "The" next level.
Think about an athlete in training, perhaps a runner. They have a training regime and a goal of running a marathon. Then their goal changes to running a marathon in less than X minutes. Then it changes again. Each time they reach a goal they set another one.
To reach each of those goals at some point they have to take their knowledge, training and exercise routine "to the next level".
Some are content just being able to run the marathon and never progress beyond that, which is absolutely fine. Others of us want more. So we work not just harder but smarter too. We maximize our efforts by not trying to do everything ourselves.
Mike, it appears your life long goal was to be able to semi-retire and you do that by owning and managing rentals. Great, wonderful. For you there is obviously no "next level".
However, I, like millions like me want more than that. We want the security of knowing if we were in an accident or fell ill our family would not suffer a drop in income just because we were unable to do the things we had done in the past. In my case it was fortunate I did that because when my wife was diagnosed with cancer I didn't have to make any uncomfortable decisions between cleaning a unit for rent and taking care of her and my son. Nor did I have to worry about it when my appendix ruptured and I was pretty much useless for physical labor for over six weeks due to the over foot long vertical incision in my abdomen.
For me, more than twenty years ago, my "next level" was reaching the point where I knew I would never have to worry about money whether I could work or not.
It had nothing to do with having a million dollars in the bank, I don't. It had nothing to do with driving expensive cars, mine is eight years old and approaching 100K miles. It has nothing do with living in a mansion, I don't. It had nothing to do with giving large sums to get buildings named after me, my wife and I have always given anonymously and I still continue that to this day. It is an incredible feeling to take my son shopping for Christmas gifts for kids who otherwise would have nothing and donate them anonymously. No receipts for tax deductions, nothing. That is the true spirit of Christmas and I get to continue to play Santa even though my son is way too old for that.
Late last year, when it was very apparent my schedule was impacting my ability to take care of my son the way *I* thought I should... It was a really good feeling knowing I could leave my job to focus on him and never once worry about anything other than him.
Sure, I miss "working" full time but I can do that once he goes off to college.
In another thread, you talked about being content with what you have. For me, it isn't a matter of being content, I have always been content and always lived below my means. But, things in this life are fleeting and your health can be taken by any number of means. You are never truly financially independent as long as your finances depend on your continued labor. That is true even if your super human abilities allowed you to manage 1000 units in only 2 hours each week. You still must be able to do the work and sooner or later there will come a time when you can't.
I have been preparing for that day for the last 24 years and that is what continues to push me to the "next level" in security and peace of mind.