[Avodah] Why should one have to make Hataras Nedarim every year?

[Micha Berger via Avodah]

On Tue, Sep 20, 2016 at 04:24:31PM +0000, Professor L. Levine via Avodah wrote:
: Note the last paragraph says "Behold I make formal declaration before
: you and I cancel from this time onward all vows,..

: In light of this, why should one have to make Hataras nedarim every
: year? It seems to me that saying it once should suffice forever.

Hararah can't be done lemafreia. It's a nice declaration of intent, but
the paragraph you're quoting isn't legally binding.

Notice that it is said /after/ the beis din was actually matir his
nedarim.

Tir'u baTov!
-Micha