How long does 1.25 units of Botox last?

Botox is the most popular procedure in my office and it sounds like you may need to have these injections adjusted.  Botox can last for three or four months deepening on the amount injected and location.  Your Botox will resolve but I would consult an expert in Botox for the best cosmetic results.  Best, Dr. Green

Hi Scala05,
I understand your concern; this must feel like your worst nightmare! However, there is hope. Effective measures may be taken to save your perfect wedding day. 
First, let's touch on what happened. I'd like to provide some suggestions to help others avoid this same situation.
Your first ever Botox treatment was performed 5 weeks before your wedding, which is risky - mostly for the reasons you are currently experiencing. We can not predict with 100% accuracy the outcome of a Botox treatment. Everyone responds differently, and unfortunately Botox can not be reversed. It is a good idea to have a trial treatment 6 months before an important event and then repeat with confidence at 2 months before your special day.  
You said your first treatment resulted in your brow being peaked, and you returned at 1 week. I ask patients to wait two weeks until the full effect of the Botox is established before performing any touch ups. Often during the second week muscles will continue to soften and no further treatment will be needed. 1.25 units sounds like a small amount, but I normally use only 0.5 units to soften a peaked brow, although I'll occasionally use more if the muscle is exceptionally strong. Then I advise to wait another full two weeks before any further adjustment.
Now to address your concern. Is it your brow or lid that is affected? Lids will improve faster than brows. Have your doctor place Iopidine drops into your eye. Many injectors will already have Iopidine in the office; it can provide significant improvement within 10 minutes for a period of 3-4 hours. If the drops work, your prayers will have been answered! Get a prescription and use it up to 4 times a day. If necessary, I will also sometimes consider injecting a very small amount of Voluma on bone above the lateral brow to act as a lift for the brow. Temple injections with dermal filler may also add some benefit by providing lift for the lateral brow. Be aware, however, that these are advanced injection techniques that require a skilled, experienced injector.
Heavy brows and heavy lids might wear off naturally in 4-6 weeks. You might be lucky doing nothing, but because of how tight your timeline is I wouldn't count on it.
To reiterate, my best advice is to get the Iopidine and use it frequently. Repeatedly work the brow muscle too, as this may accelerate earlier return to normal.
I hope this works so you can relax, be confident, and enjoy this very special time with your friends, family and future husband. Best of luck!