For changing the bag, depending on how fucking nasty it is, I'd say every 2 days. If it's loose or leaking, change that shit, cuz man, the acids in your feces are gonna fuck up your skin. If it's your kid with an ileostomy, or just an ostomy in general, they might start to get fussy or uncomfortable, or if they're older, they might complain that it's itchy or it burns. That's when THIS occurs. So change that bag, okay?
For emptying, wich you do a handful of times a day, also depending, I keep a pair of plastic gloves in the Water Closet that I slip on for these special occasions. I'm such a fancy lady, emptying my shit-bags with gloves on.
With the Coloplast ones I have here, I unroll it from its delightful velcro wings (seriously, velcro wings on the flange are the greatest. So much fucking better than the clips) and squeeze it open at both ends so the hard plastic remains open while I drain it.