1993 GMC C1500 A/C Compressor cycling

The air conditioner is cooling as it always has, but A/C compressor is cycling on and off more frequently. Once the inside of the truck cool down, the compressor will cycle on and off every 5 seconds at idle and every couple of seconds at higher RPM. I had heard that the system may be low on R12, but it cools like it always has. I still had a can of R12 and went ahead and added some. It took about 1/2-2/3 of a can. Didn't help, it still cycles rapidly.

I have this truck since new and I know this compressor is suppose to cycle, but it seems to be doing more than it used to. Am I just hearing more things as this truck gets older or is this normal?

Thanks for any help.

Tom