index files still growing

Hello,

I am using Postgresql 7.0.2
The problem is that my index files are still growing.
( and I vacuum each night !! )
My solution is to DROP & CREATE my indexes files once
a week.

Is this a known problem with 7.0.2 ??
Is it solved in 7.1.3 ??

I spent an hour on deja.com without finding any answer.

Any idea ??
Thanks.

Pierre.