In my experience, it takes a LOT longer to convert no deposit offers into real money players. That being said, IMO, it will happen….it is a numbers game. The more signups you get, the more chances you have of getting depositors.
Four years or so ago, when I started in the gaming business, it took atleast a year to see any profit from no deposit offers…but the numbers and deposits steadily increased. So if you are in it for the long haul, I would suggest a combination of no deposit and match deposit bonuses….with your main page offering only a few nd’s and a seperate page for the rest of the nds. All just opinion here, and everyone has a different experience in the field.