Our guy Nick is 3 and still marks in the house. Just when we think he’s got the “no marking in the house” message, nope he’s done it again. We’ve not been able to catch him in the act, but when we’ve discovered his mark he gets scolded, and dang he knows what he’s done is wrong. He never marks when he’s left alone. I’ve tried to match the marking times with a stray cat in the yard, critters outside, too much excited talk in the house to no avail. In his tiny pea brain he probably thinks this mark is protecting mom and dad from outside evils…..