That's why I posted that link about the body found wrapped in multiple layers of plastic in a small apartment - it apparently didn't produce much or any odor for quite some time.
I'm not suggesting that the body is still in an apartment - but the person would have had at least 2-3 weeks to move it. Or to skip town. The odors might still be contained mostly inside an apartment (esp in a bathroom) as long as the rent was paid.
Anyway, there are a series of this type of body disposal (mostly in single family homes - but what's odd is that sometimes even the other family members are not smelling much at a month or so out).
Here's a case where the deceased was thought to have been murdered in July and remained in an apartment undetected until November:
The victim — Heather Schwab, age 35 — had been reported missing back in June by her estranged mother, who told cops that she hadn’t spoken to her daughter in a year
nypost.com
The perpetrator took several precautions - but this is not the only case of that type.
Just trying to think of every possibility!
JMO.