Will kerosene reserves deplete long before oil? Assuming that the oil reserves would end at a certain date, would it be expected that the kerosene be no longer used as fuel on a previous date due to the quality fall of barrels?

If so, would that date be much more previous in absolute or relative terms?
No.

At the moment, we use cracking to turn heavy, long-chain hydrocarbons into more valuable short-chain hydrocarbons, such as petrol/gasoline and kerosene; as a general rule, lighter hydrocarbons are more valuable, at least up to butane.

Generally, it might take the form:

C$_{16}$H$_{34}$ $\ce{-&gt;}$ 2 C$_8$H$_{18}$  (Octane, a typical petrol component)

Note that this is not balanced; to crack to fully-saturated products we need to add hydrogen, usually made from natural gas and water. This is why you sometimes see that a refinery will take 1 tonne of heavy crude and make 1.1 tonnes of petroleum products. This is called 'refinery gain'. 

Essentially, as long as we have hydrocarbon feedstocks, we can make kerosene.