Onion sets - how much watering, and how long till they come above ground?

[zazen999]

I'd dig them all up and not worry about the root development; and put them in with the tips just poking out.

[PrideRavyn]

Thanks guys, the onions have now been repositioned! A few were further on than the ones I hoofed up, with a fair amount of roots underneath, so I am just hoping now that they don't die from the disruption.

I was thinking about planting more just in case they don't like the move, but I have pretty much used up most of my space with other things. I have some fairly shallow (about 5 inches) containers that I could fill with soil/compost. Would these be deep enough for onions?