What exactly are your trying to control 40' away?

I'm assuming you have the T2 Remote to go with your IRF-6. (WHich has only 6 IR outputs... hence the name)

THis remote will output both RF AND IR for local componants. Quite often I have the equipment remote mounted being controlled RF while the TV is being controlled IR.

I'd worry more about your RF range than the lenght of the Emmitter leads. The IRF-6 has plenty of output to run 50+ feet of emmitter lead, but I have terrible luck with RF over 20-30 feet.