I don't think they are ready. I'm not sure why, but most of what I read says it takes like a week of hanging to be dry. In my experience, my plants are dry enough to jar within 3 days, sometimes a bit longer. I like my buds a little on the sticky side though. I guess it depends on the temp and humidity in your drying area. Also depends on the density of the buds. I have a small oscillating fan that I use and it helps a lot. Also, as long as they dry enough when you jar, you only really need to burp them for a few days.
Basically, I jar them when the outside feels dry. IMO waiting til the stems get brittle and snap is too dry. After 12-24 in the jars, the remaining moisture rehydrates the outside. That's when I burp and leave the jar lid open for a few hours. I repeat this cycle until they are the point where I like them. I really don't smoke all that much, so my jars get opened a lot until it's gone. I'd rather have them a LITTLE too moist than too dry. It isn't really something you can set your watch to, but if you harvest a week before you have to leave that should give you plenty of time to dry, jar, and burp to the point where you can leave them in the jars for few weeks you will be gone. Hope this helps.