I once worked for a man who told me that people were like jars of marbles. On his desk were three baby food jars filled and partly filled with various marbles. "You can only fit so many marbles into a jar." He explained, you can also only fit so much into the human brain. If you want to put in a different marble into a filled jar you have to take another marble out first.
In one sense this seemed logical to me. I have read that the synapses/neurons of the brain grow madly while the human is in utero but after the age of around 18 months the unused ones begin to die off and you're sort of stuck with what you've got. I've also heard that brain cells do not repair themselves. Of course skin cells do. And, naturally, through regular maintenance, the cells in my body now are not the same ones I was born with. Apparently those brain cells manage to at least reproduce themselves and retain most of the old memories. They also accommodate a ton of new information on a daily basis.
While I appreciate the concept of limits, it bothers me when those limits become restraints.