Sathi haru ho....payincha ki payinna??

yo december ma nepal jaauki bhanera sochya....khai kasle k bhancha kasle k....My visa expires on May 08, but got I 20 until 2010... will there be any problem if i go nepal this december? coz .. i hear people say that if my visa expires less than six months that i land in Nepal then i won't be able to come back .......what's the the correct procedure or law. Will there be any trouble??