14 days was mentioned by Ravna, that is who my post was addressed to.
Now, for your skin issue - I use the same ostomy bag as you do(the first one on the left of your pictures) but I add a Adapt CeraRing Barrier Ring to the hole/the opening, before sticking it on me. You did not put up a photo of that item so I thought I would ask if you do? That has provided me with a perfect seal, never a leak. I have had a skin inflammation similar to yours but only in the summer in Phoenix because I am outside with my horses and sweating. I learned the "crusting"technique and it worked perfectly, quickly too. If you are interested, go to YouTube and search for "ostomy skin irritation treatment", it is a lot of extremely useful information and technique videos. Well worth the research!