thats easy to do 40 lvls in 2 days. basically buy yerself the best armor (def) you can, always upgrade yer weapon when you can to the best. and lastly, use a n/c hack. i pulled 45 lvls in 3 days.
if using a hack, be smart about it and dont go into places that are crowded. also use dungeons! thats where you will get the best exp. if yer armor is good enough you will be taking 5-10 mobs at once and mowing them down with yer 8 slot weapon at +10.
(btw, this is granted you have gold to buy the best equipment.)
hope this helped out.
