Depends...
Shooting a heavy bow (>70# @ 30") for a number of years exclusively, I found that I couldn't shoot a lightweight bow (<50# @ 30") accurately. But I realized that the heavy bow had taught me some bad habits within my release. The heavy bow almost rips the string off your fingers and with the light bow you need to actually release the string consistantly.
So, I now shoot both. Light weight to work on form and release, which carries over to my form and release with the heavy bows. If you are having trouble shooting a lighter bow accurately take a little self assessment on your release and form and the accuracy will come around with the light bow, and actually help your overall shooting even with the heavy bows.