Then there’s also this to consider, Your Place in the DRO REVIEW, DRO HEARING or BVA HEARING LINE.
I’d file the NOD Today for a DRO or BVA Hearing, plenty of time to get the IMO and any other Compelling N & M Evidence submitted, 2 to 3 yrs on the DRO and 4 to 5 yrs on the BVA depending on the type of BVA Hearing you opt for. Of course, the sooner the better with the Evidence. You might end up getting an RO Award based strictly on your New Evidence.
The DRO Review is a different story, if the IMO is expected in the next few months, probably not a problem. Failure to get the IMO or any other N & M Evidence submitted prior to the actual DRO Review would result in an Administrative Denial by the DRO.
You never know when the DRO Review is scheduled or completed. The 1st indication will be either a RETRO Award Deposit or a Denial SOC Letter. BE CAREFUL!