It depends on the moisture content still in the buds. If you're still inside the first week to ten days of jar-curing, I'd say opening for 10-20 minutes, 4-6 times per day should be okay. But again, it depends on exactly how dry everything was before jarring, and your personal preference as far as moist/dry weed.Give the buds a good squeeze to check moisture content, and if it seems to be going well, you can open only 1-3 times a day for a shorter period. The main thing to be careful of during this time is moisture trapped inside the buds that could possibly lead to mold in a few days if not checked well. Just remember, if it feels all crunchy and dry on the outside, that may not necessarily be the case on the inside of the buds. Better to overdry a bit and add a stem or leaf to replenish a bit of moisture, than to presume it's dry and end up with moldy, useless smoke in a week or so.