Everyone stains differently and every stain is unique.
The soles and palms stain the darkest and last the longest
as the skin is thickest there,
 thereby, it takes longer for your skin to exfoliate.
The further you move from your hands and feet,
 the lighter and the less time your stain will last.
Backs and chests, although they look cool very often only last for  3-5days.
Below I have documented the staining of my hand
deisgn from paste to a week later.

This is design paste freshly applied


Design courtesy of Hennatribe

After wrapping and sleeping with wrap over my hand this is what my stain looked like

Here's the design approximately 36hours after paste application

Same design seven days later

This is the same stain 15 days from application