under normal conditions

Depends on the Wax....Some will last longer than others. Maybe 3,6,12 months. It'll also depend on how many coats you put on along with other variables

ok i used eagle one wet like 2 weeks ago.....it shines nice...but the surface feels rough (not as smooth when i applied)...it also seems to attract alot of dust....should i wash/wax my car again or just leave it as it is through fall/winter then wash around march/april?

the best wax i have EVER used is meguiar's 3 step wax
takes FOREVER
but worth it
comes out looking SHOWROOM
!!!!!