I'll try those ideas soon, thanks.

Another thought...
I'm running the 16F628A at 5.0V DC. After looking at the electrical information, it seems that I should be running it at 3.5V. This would run the internal oscillator at a more precise speed. Is this correct?

Please make sure I'm getting this right.
5V supply... 3.5V drop across the PIC... Voltage drop of 1.5V... PIC runs at 150mA
R = V / I
R = 1.5 / .15
R = 10 ohms (1/4 watt)