Second run with butane will pull more impurities than desirables. If you truly want to pull more thc from spent material do a ethanol wash, winterize, and use the oil for edibles. Ethanol wash still won't yield much but it's worth it if you have lots of garbage material.
The only people I know that are running material multiple times are the same kind of G's who are just making profit bho to be sold N the skreetz yahearrd!