I keep about 1/2" of space so the albums are easy to slide out. Most of the time I get rid of the poly covers - they are difficult to slide and in my opinion, could damage the cover. I've also begun to thin the collection.
I don't know how he stores his records, but a friend, I'll call him One-A-Day bought his first TT from me in March of 2011. This KD-650 developed a hitch in its tonearm and he brought it over and I repaired the tired bearing race and retorqued the horizontal bearing. All was good and off he went.
I have been keeping track of his album purchase numbers and although he moved to Seattle without his gear in Sept, it did not slow down his record buying. When he was here a couple weeks ago to grab his gear from storage, he mentioned he has about 760 albums now. About 1 a day by my count.
He is going to need to investigate storage options as I don't see any slowdown in his collecting.
Lemme update this story. One-A-Day was more than up to the task in the new environs of Seattle with new stores and new music to investigate and in the first 3500 days from buying his first turntable he had amassed 4500 records. Then he changed directions. He decided to downsize and has unloaded all but a handful of records, divesting himself of nearly all his rig. Kept some headphone gear. Since he was prior to a vinyl accumulator, a polycarbonate collector, I received about 1000 CDs from him during the purge. He seems much happier now, knowing he can put his belongings in his FJ and roll if he wants. He won't need to but he can if he wants.
Since he started buying in about 2011 and sold in 2019, he made some good money with the price increases we have seen in used records and the deals he got when he first started buying.
As to the proper amount of pressure to have on the albums in the rack, you can compress them if you have to because the label and outer edge are raised and will keep the grooves from getting hit. On the other side, loosely packed, as long as the records are nearly vertical they should be fine and not develop warps from being stacked in a slanted position. Unless there is enough pressure or it is hot enough, the records won't change shape easily. I guess the left coast needs to be careful with the heat this summer but a bit of a tilt and having room to get records in and out easily should be the way to go for convenience and no damage.