You didn’t mention how long your stats are. In my experience you can expect approx 25% off when staying for one month +. You can negotiate some other benefits like 25% off F&B and up to 50% off laundry.
The longer your stay, the greater the discount achievable. Another negotiation factor can be prepayment, if you prepay 100% of your stay, the hotel will be more flexible to provide a discount since they will always be concerned about an early check-out before the agreed length of stay.
Negotiation can be started at the reservations office contact and then you can push to escalate up all the way to GM level.