PaulH wrote:
If I file an IFR flight plan 2 hours in advance from departure from a
towered airport and then leave really early or really late:
1. Is the FP normally available to my local tower about half an hour
after filing?

The FP is there 30 minutes prior to your P time. When you file is not
relavant. If you want to leave earlier than 30 minutes before your P
time the controller will go into the computer and type in this...AM
N12345 tim Pxx00 That tells the computer to change the P time to the
current time, thus generating the strip for the controller so he can
read you your clearance.

2. How long does it remain in the "system" if I get delayed?

The default is two hours after the P time. In some very busy locations
they may shorten this up to free up some more transponder codes.