I think that one of the most telling things about RH uncovered in the infantile stages of this investigations is how he obsessively holds on to things.
Aside from being an apparent packrat (evidenced by his crowded house of belongings), holding onto his grandfather's WH belt, the appearance of his childhood house which was stated he was trying to preserve as it was the way his parents were alive and not keep up or change or even renovate, and reports of his car that was messy and filled with papers and junk - the most telling in my opinion is the first generation Forest Green Chevy Avalanche. I mean he used this car to pickup Amber (it was identified by her roommate Dave) and most likely used to pick up the other girls as well and then sadly transport their bodies to Ocean Parkway. It would be riddled with their DNA. It should have been his biggest worry being parked outside of his house - yet he doesn't get rid of it or ditch or sink it or burn it. He sells it to his brother down in SC. Keeps a tie to it, even though he knows it could be incriminating one day. It represents attachment to these girls, his trophies, his victories, that Forest Green Avalanche is something that represented fond memories that he simply refused to part with even if someday it comes back to haunt him. More so, he then has the gaul to replace that first generation Forest Green Chevy Avalanche with a new black Avalanche - probably for all the same reasons and associations. This new Avalanche was vital to the investigator in term of narrowing him down IMO. They knew the killer drove an Avalanche years and years ago as it was identified by Schaller (Ambers roommate who also gave the crucial 'Ogre-like' description), they had cell tower pings from midtown Manhattan and Massapequa, and they knew he was Ogre-like. A simple car search for Chevy Avalanches registered to Massapequa address in 2007-2009 or even currently was the break in the case, then getting a visual on him and seeing his size and sort of lumbering body type - Ogre, boom. Dig deeper, he works in Manhattan a few blocks from the other cell tower pings. Dig deeper, his wife is out of town at time of murders. Collect His DNA from a garbage pail in NYC, and collect his wife’s DNA from bottles left in their recycling bin, and it’s case closed. It all starts with the Avalanche though, the cell tower pings in NYC and Massapequa were previously known about for years and even public knowledge - but not enough to go on or narrow anyone down but the Avalanche info revisited by the Task Force was what lead them to that house, and be seen as Ogre-like, to be uncovered as a commuter that worked near the NYC cell tower pings. What could have initially been a cursory PO drive by the house as someone in a larger group of people who owned a Avalanche and lived near the Massapequa cell tower quickly snowballed and snowballed and having a new Avalanche in the driveway might have put him on top of the list to dig deeper with.
If he held onto the Avalanche; the single most incriminating, DNA holding, and easily identified object from his killing days, he held onto more than just the memories of those four girls. There has to be some of the missing possessions from the Gilgo 4 girls in that house. Not in storage, not in his office, not in his car - but in that house and probably close to wear he puts his head down to rest at night. This was obsession. Just like other addicts that can't cut ties with things like drugs or alcohol or gambling that they know are damning, the Avalanche represents that for Rex Andrew Heuermann and I'm sure there's more. More mementos from the victims, more clusters of burial sites (his trophy cases), more evil incarnate.