It certainly does help sales, however... I would offer advice that if your only target is number of listings you may be heading for disappointment. Its really important (I think more important) to make sure everything else is improving as you grow too, i.e. great pictures, proper pricing, enticing and informative descriptions, looking professional etc etc. If you don't do this then its going to be very hard to update and improve 100 listings, rather than , say, 50!
This is just a general observation btw... not aimed at anyone in particular!