sadly, yes.
Do you live in high humidity area? the added moisture will make beer out of your McCanns with the airborn yeast if you're not careful.
Oh, btw, here's a tip with Steelcut oats, in case you didnt already know: toast them. Dump the whole container into a glass caserole and toast them at 350f, mixing/stirring them every few minutes until they get deep golden brown. Let them cool and then back into the can.
You will FREAK at how wonderful this makes them taste, and the added benefit is that it cuts the cooking time in half or more.
cheers.
.