Flexible nibs: Use and abuse
Flexible nibs can be a joy, but it is important not to push them too far. Too much pressure will provide dramatic line variation, but will also ruin a nib in short order. A nib that would have lasted a lifetime can easily be rendered useless in a matter of days or weeks, left distorted, fatigued, and prone to cracks.
Many writers assume that a nib that yields with light pressure was intended to be used aggressively. In most cases, it was quite the opposite: very flexible nibs were recommended for those with a very light touch.