Just another onion question
 

I finally went outside and looked at my garden boxes today- and, woo, my lettuces are finally sprouting and coming above ground! I got a better germination rate than I thought, and i'll definitely be doing some thinning out when the time comes.

However, i planted onion sets at the same time- some in each of my garden boxes (to help ward off insects, etc) but none of them seem to be sprouting. Am I being too impatient? I put the lettuce and the onions in ground at the same time, roughly 2 and a half weeks ago. How long should I wait for the onions to show above ground before i should plant some more sets, and consider the older plantings a loss? I'm still new to the whole onion thing, and while my seedlings inside are doing well, I'm lost on the onions!

I may have put the first planting too deep, and fixed that by laying another set closer to the surface in another box- I figure at least one of them will come up.