WCT,
There are a couple of points to know about Primary/Secondary/Reserves.
1. Only Primaries can SAP, and get their blocks first, two months in advance.
2. Secondaries get their blocks after, which means that they get a mixed bag of left-overs from Primaries.
3. Because Sat., Sun. and some holidays are restricted for everyone, some people believe that bidding RSV during certain months is beneficial.
4. AIL is going on the bid sheet for everyone, and it is for the next day's trip. Scheduling starts covering at noon for BHs and 1500 for RSVs.
5. Primary positions can not be taken away by a more senior person unlike SAP, AIL, SWAP, ETB, and secondary trips.
Hope that helps.