The amount of principle required to sustain $1 of annual real consumption in perpetuity costs between $25 and $35. $50 is far beyond enough - you'll die with far more money than you started with.
That is presuming you weren't essentially forced to pay this early to help your kids in the first place. Say, housing, education (incl. extracurricular), incidentals.
The truth is, most people can barely afford to save due to aforementioned high costs.