I ordered my unit a Christmas time. Dealership was very slow and welcomed the cash flow. My unit arrived 30 days later.
For me it worked out well. Factory is slower as well so units are not as rushed out the door.
It allows a lot of time to slowly test the unit and deal with any warranty issues prior to the start of camping season.
I would not base my timing on when to start paying for the RV, but I would consider when I can start using RV. Allow time for glitches and delays.
February is fine for the Philly area. February allows times for glitches and delays. By March and April things are starting to get going. You want to have everything sorted out and usable by March.