FAA staffing on the local facility level is mostly determined on a case-by-case and day-to-day basis. You can be told a facility is not available to you today, but it's available to somebody else tomorrow. I have learned this in 25 years in the FAA. It's who you know that counts. This fact has worked for me and against me in the past. Every 5 to 10 years the calculation method for staffing levels has changed, too. Advice used to be to always take first offer, get FPL at first facility, then "pay back" facility by spending FPL time there equal to the time you spent in training there. This has probably changed, too. Work hard, be patient, and make your current facility a fun, learning environment. Use your connections to get where you want to be.