Once a week is nothing, if you actually view it as a job, and actually make a fair wage doing it. I'd consider that routine work for any band. You could very well be "good enough" playing once a month, but there isn't a musical group in the world that would actually play better at gigs practicing once a month than they would practicing once a week. If I was truly a professional musician, I'd have my instrument in my hand at least 6 hours a day, maybe more, without complaint. I'd consider myself blessed to have that for a job. If you've been doing it for 10 years without personnel changes? Maybe you can ease off a bit, so the members can focus on their other jobs. But I view true musical professionalism of attitude and work ethic as spending 30 to 40 hours a week minimum with your instrument in your hand, some of which should be with your band, if you're in one permanently.