Good topic, Blue. I think it's a question that many bands, and many musicians, struggle with if you are anywhere in a category other than "I am a full-on professional and this is all I do and I make plenty of money doing it so I don't have to do anything else" (in which case, you've already committed to it fully).
As far as being committed, some nights I feel like I need to be.
Our band has fought with this and I still wrestle with it personally. Being in a gigging band takes a HUGE commitment. Practicing, scheduling shows, meetings, making demos or recordings (did that fun little thing last night....), it all means that you have to make choices about what you want to do with your time. What you will decide is, in my opinion, directly impacted by how much you like being in a band (notice I did not say "playing music"). But in order for a gigging band to be successful, there have to be a few things; there has to be direction and a common goal that all the members share, there has to be a common expectation for quality of performance, and there has to be comparable musicianship among the members. If you have these things, and the members are mature and serious about what they are doing and have experience doing it, the commitment sort of becomes understood among the group I think.
When we have had members who were unable to provide the commitment necessary to do what we are doing and wanted to do, we handled it as a group by addressing the situation with them and asking them to be honest with us and with themselves about whether they could make the commitment. That means doing a lot of your own homework and managing your own time without being with the band at the practice space. Which can be tough when you are juggling a full time job, a family, other hobbies, and personal time. In every case, the person who was not carrying their share of the load either left or was fired. I keep in contact with all of them and to the person they are much happier without the obligation in their life because what was required was more than what they were willing to put in as far as effort.
The one thing I have learned; if you have to ask about commitment or explain it to someone.....they are either rookies (not a bad thing, we all started somewhere and made the same mistakes) or they won't make the commitment anyway. Anyone with experience doing this understands the requirements and doesn't need the explanation. And all it takes is playing with one successful gigging band to learn all you need to know about the whole commitment thing. Then there's the question you have to ask yourself about whether or not you really want to make that commitment.