I remember a study done a while back that found there are kind of "islands" of wait time that are acceptable, and "valleys" that are annoying.
I can't recall the numbers, but it was something like under xxxms was consitered "instant" and therefore wasn't an annoyance, from xxxms to 1 second is consitered annoying because it's too slow to be "instant" but not slow enough to let you context switch. Then from like 3-5 seconds was another "island" as it's enough time to context switch then return.
The end of the study found that by delaying some actions that were in the "valley" to be slightly longer and making them consistent it was reducing frustration while using the application.
I can't recall the numbers, but it was something like under xxxms was consitered "instant" and therefore wasn't an annoyance, from xxxms to 1 second is consitered annoying because it's too slow to be "instant" but not slow enough to let you context switch. Then from like 3-5 seconds was another "island" as it's enough time to context switch then return.
The end of the study found that by delaying some actions that were in the "valley" to be slightly longer and making them consistent it was reducing frustration while using the application.