Why do drugs which are hormones have long half-life?
The question is a bit vague, but in general a drug formulation is made of the active principle plus a series of other non-active compounds call excipients.

Excipients have multiple roles such as:


They act as fillers to add volume to the drug. Often only very small amounts of the active compound are present in each pill/capsule/etc. and it would be complicated for the patient to handle these very small amounts.
They act as binders to keep everything together and avoid the pill to crumble.
They can modify the pharmacokinetics of the active principle by speeding up or slowing down its release.


(there are many more resons to add excipients, see the relevant Wikipedia page for a longer list)

This last point is what you are looking for. If the hormone (or any other molecule, it doesn't really matter) is complexed with excipients it will be released in the blood or metabolized slower/faster depending on the specific molecules/formulations/mode of administration.