I've always wondered if there would be any issue with not doing it at all. Financially, it would look as if tons of theft occurred; it looks bad on paper. But in reality, it doesn't matter if the computer thinks I have 200 bottles of vanilla or 2, as long as I have enough to serve drinks until the next order comes in. I would love an answer to this question because it just seems like a complete waste of time.
There were times where I was the Starbucks closer and had to do the entire inventory (for Starbucks, Food Ave, and the photo kiosk) while being the only person behind the bar and also worry about closing. For beverage ingredients, I wrote down an approximate number 2-3 days in advance because I always knew about how much I had on hand at any given time. For sellable merchandise, I'd just scan the item and enter in the number that it said we had. Those numbers are going to be very very close anyway, and I'm not going to stress out over it if they give me literally zero hours to do my counts.
Also, I did one last August and forgot to count the pastries. Oops. No one said a word, although my TL probably noticed how far off the counts were when she did inventory in November.