Question about when to WILD

I know that the preferred times to try a WILD are during a WBTB or during a nap, so I need to know if there's a maximum number of hours you can wait before taking the nap. I wake up at like 7:30, go to school, come back home at around 4, and then take a nap. If that isn't too long of a time to wait, what is? And potentially if the wait time is long enough, if you went to sleep at a relatively early time after having a nap, wouldn't it have potentially the same effect as an afternoon nap?