If you are cycling your tank with fish, you should be changing the water every day, around 25-50% of it at least. You need to keep your ammonia levels below .5 (preferably below .25) to keep it safe for your fish. If you let it go, your fish (at least some of them) are most likely going to end up dead.
It will take a couple of weeks of daily partial water changes before the nitrifying bacteria gain a foot hold and can start successfully converting the ammonia to nitrite, and then eventually to nitrate.
Ammonia lock has little effect on this... if you are cycling correctly and maintaining a good partial water change schedule, you won't need it at all.
Generally speaking, chemical additives for fish tanks (with the exception of a good dechlorinator) are sold to beginners who don't know any better. Most veteran fish keepers will tell you it is best to not use ammonia lock, pH adjusters, water clarifiers, algaecides, etc. These products mask problems - they don't fix them. It is much better to uncover the cause of the issue, and fix that, so that there is no need for a band aid.
In the case of cycling a tank, constant partial water changes are the best course of action, rather than ammonia lock.