The process of baiting for termites is highly variable. 

Sometimes much of the time is spent getting them into the baits.  Sometimes they're in by day two.

Some bait toxins take several weeks or months to noticeably affect the colony.  This is especially true of the hormonal approaches.  Some toxins will usually kill off a colony within two to three weeks of the first feeding.

Some termites are bait shy and may take weeks or months to return to a disturbed bait.  Some termite species don't share very well, so with them the toxin takes much longer to reach through the colony.

If you are using a commercial bait system, the supplied information should be able to tell you roughly how long things should take.  If you don't know, ask.  The technician's job is to (i) manage the termites and (ii) communicate the process steps.

In some risk situations, baiting may become a permanent process.

Don't assume that because a lot of termites have been killed there won't be other (colonies) ready to move in an take up the attack.

After any baiting program, an inspection program is necessary.