Yes, ISTPs can commit, especially with partners that understand their introverted nature and provide them plenty of alone time, and the partners that are also able to handle the ISTP's soft-spoken, easygoing personality are likely to get them to commit rather easily. It is a myth that the ISTPs can be somewhat flighty and may not commit easily, because in reality they may commit long-term to somebody that also wants to commit to the long-term and is able to understand them enough.