Desire = f(t).h(n)

Until fulfilled, human desire is a function of time. This statement can be expressed as given below:

Desire = function(time)
=> Desire = f(t) ----- (1)

f(t) can decrease with time => Desire can decrease over a period time. E.g. A certain type of food you want to eat
f(t) can be a constant => Desire can be a constant E.g. A place that you always wanted to visit.
f(t) can increase with time => Desire can increase over a period time. E.g. A professional post that you want to occupy.

The increase, decrease and consistency of desire depend on human nature or idiosyncrasy. Hence we can say desire is also a function the human nature who owes it. This would draw the following eqaution

Desire = function(human nature)
=> Desire = h(n) ----- (2)

From equation (1) and (2) we can conclude

Desire = f(t).h(n) ----- (3)

Once its objective is met, Desire dies. It can give way to new Desires; but definitely it dies once it reaches its destiny.