The reason I added the calls in Teleop was because the single call in Begin wasn't enabling the compressor. I tried calling it once, and it just didn't enable. So then I called it in the loop. And it worked. So I left it.
Code:
relay8_fwd = !rc_dig_in18;
This is what IFI had for their compressor. WPI has:
Compressor->Open, which opens two RT-FIFO's and a Digital Input and a Relay, then begins asynchronous execution of a thread dedicated to polling the compressor.
Comrpessor->Run (thread) - polls compressor as fast as possible, assuming no delays from RT-FIFO (greg claims it does wait for new data).
Compressor->Start - sets RT-FIFO to enabled
Compressor->Stop - sets RT-FIFO to disabled
Compressor->Enabled - gets RT-FIFO for enabled and switch state
Compressor->Close - Closes RT-FIFO. The Run thread closes itself when RT-FIFO spits an error out (assuming that the RT-FIFO was closed).
All the complexity to take the place of that one line of code.