(2) An extension in the flight duty period under paragraph (a)(1) of this section of more than 30 minutes may occur only once prior to receiving a rest period described in § 117.25(b).

It’s certainly not legal to just expect the extension every day beyond the beyond 30 minutes. You can’t accept more than one before you get 30 hours off. That part is pretty clear. No interpretation needed. Refer dispatch to this CFR if they try to pressure you into it.