shiro, it's perfectly okay to be constantly changing your fursona. it's reasonable to want to change something. it makes sense though. we, ourselves are changing all the time internally. if we're changing our personality and ourselves, doesn't it make sense that we would want an external change as well? so it only makes sense that changes would happen. i would no fret it too much, and just change your fursona as you please *nod nod*
you're going to be a different individual two years from now, even if slightly. now doesn't it make sense that your self-image will change in that span of time too?
*gives a thumbs up and a grin* don't worry, good buddeh! it's okay to keep changing your look.