Is Kovea Ittim only for the wealthy and brilliant?

What gets people to stick with their learning after many years?
What’s a valid reason to miss your Kevius?
Does someone who gets paid for learning or teaching additionally need to be Kovea Ittim?
Can the Kevius change over time, like when more children are born?
What if a wife needs her husband during his learning?
Do you need to lose business/clients as a result of your learning?
Should you answer calls from clients or your boss during learning?