Is it ok for a Christian to live in sin?

There are some Christians who willingly live in sin and know that they are doing wrong, but do not care.  Many come up with the excuse that since they cannot lose their salvation and God’s grace covers all sin that we are free to do whatever we want.  The problem is that Paul, through the Holy Spirit, foresaw this and has countered it already.  Paul asks how can we that are dead to sin live any longer therein (Romans 6:2)?  We are not to serve sin, because we are free from sin (Romans 6:6-7).  As Christians we are to put our flesh into subjection daily and strive to live a holy life pleasing to God (2 Corinthians 10:5).