This works two ways...
Typically, your requests are filled by seniorty of the date you booked your reservation NOT the date you added the requests. There really isn't a good way to know when requests are added.
Catch!!! (I am speaking from my front desk experience alone) If you call an add requests after the rooms have been pre-assigned by the room assigner, you have a lesser chance of getting your requests.
Example: At OKW, when I was there, we blocked special requests for view, location, etc. 5 days before the arrival.
So everything with a special request is blocked for 5 days from now. A member calls and is arriving tomorrow or two days from now or three days from now...basically anything that has already been assigned. This member booked their reservation 11 months from their arrival date. They did not have any special requests on their reservation except that they want non smoking (which they have been assigned to). They suddenly decide they want to be on the first floor close to the hospitality house. Unless there is an unblocked room to change this to, it is simply not feasible to reblock everyone arriving for the next few days to accomodate this request.
This is when the resort will put a note in the reservation that "member called to request hospitality house the day before arrival". This request would then have low seniority.
I cannot say this is how every resort does this, nor can I say this is still how OKW does this, but this is how most room assigners approached this situation when I was there.
My entire point is, if you want to make special requests, it is a good idea to call MS at least 1 week before your arrival. This way the resort will have no clue that you just made your requests recently.