This question about why the longer esters take longer to "kick in" is not a simple x causes y answer. I will do my best to explain it the way I understand it and I hope it will make sense for you as well..

Each type of test has its benefits and its drawbacks. All test kicks in immediately, but the noticable effect is signaled by the conversion of test either by way of the dht pathway or the estrogen pathway. Which is why some "kick in" faster than others, they are unbound from the ester and converted/metabolized faster (shorter esters). You "feel it" because the dht receptors are being activated due to test being metabolized BUT the masculizing effects begin when the ester binds w/the androgen receptor.

Whats this means is: Protien synthesis begins basicly the same time no matter which test you use BUT it can take our bodies weeks to produce enough androgen receptors to be able to use all of the test injected.

So in summary, the longer the ester the longer it takes to bind with our androgen receptors PLUS the time it takes for your body to make enough receptors to take advantage of all the test injected EQUALS the longer "kick in" time for the different esters.

Hope this helped.