During the off months, not having an item in stock hurts.
During the busy months, something else will sell instead.
But it is always slightly nerve-wracking, because you can't be totally, entirely sure that they'll show up. Christmas is also like this: but, as I always end up finding, they haven't canceled Christmas, yet. They haven't canceled Summer, yet.
It took me a long time to realize that my sales would happen because of what I have in stock JUST BEFORE the season starts; not after the season starts. In fact, ordering lots of material in the busy season just leaves that material and the leftover bills for Fall, the slow season.
So, now I just sort of sit back and hope for the best, and relax and enjoy the weather, take time off for vacations, and let nature take it's course.
P.S. I just realized this is my 2000 post. Haven't missed a day.