Why on earth do we need new actors in the future???

[norsecode]

I keep hearing people say that if the movies aren't filmed one a year 
for the next seven years, that we won't be able to use the same 
actors (i.e. Daniel Radcliffe, Rupert Grint, and Emma Watson).  Some 
even suggest that they'll have to be recast before book 4 or 5 are 
put on film, even if they DO film one a year.

I don't understand this.  Dan was 11 when he played 11-year-old Harry 
last year.  He's 12 now and is currently playing 12-year-old Harry.  
What is the problem here?  Why on earth is it a problem that he is 
going through puberty and his voice is changing??  OBVIOUSLY boys DO 
mature at that age if Dan is doing it.  Who's to say Harry didn't do 
so at age 12 too??

And Rupert Grint is one year older that what he's been playing (he 
was 12 when he played 11-year-old Ron, and is 13 as he now plays 12-
year-old Ron) and Emma Watson is one year younger (she was 10 when he 
played 11-year-old Hermione, and is 11 as he now plays 12-year-old 
Hermione).  Will one year more or less make that much of a 
difference??

Moreover, I fail to understand why people are so worried about these 
actors "aging."  I mean, look at all the actors over 20 out there who 
are playing teenagers.  Prime example: Tom Welington, who plays 13-
year-old (!!!) Clark Kent on "Smallville," is 24 years old!!!  
Granted, he certainly doesn't LOOK 13, but he can get by.  Or, look 
at Scott Wolf who played 15-year-old Bailey on "Party of Five" when 
he was in his late twenties!  At the same time, Matthew Fox, who 
played Bailey's 19-year-old brother was in his mid-twenties.  Look at 
all the actors on just about any teenage laden prime time soap.  
In "Beverly Hills 90210," Gabrielle Cartis was over 30 when she 
played a teenager, and most of the rest of the cast were in their 
20s.  Playing younger than one is has never been a problem in 
Hollywood.

Kids grow up.. it happens in the book just as it will happen in real 
life.   So what if by the time book seven is filmed, instead of being 
17 Dan is 20.. or even 23.. (oh the horror!).  Do we really care?  
Wouldn't we rather see him play Harry Potter in all 7 movies than 
have to deal with changes in cast??

Dawn