I'm another pull fortnightly guy. I pulled weekly for reps for six months trying to break 600 lbs, my DL max went nowhere. I got better at reps though. Started pulling heavy fortnightly again and I added 15 lbs to my max in about six weeks, getting my 600 lbs.
I definitely work better if do a DL variation every week, but only pull heavy every 10-14 days. Squats twice a week are necessary for me, though. Once heavy, once less heavy.
I think if you're pulling below 440 lbs, multiple DL days per week may work better, but once you're closing in on or passing 500 lbs heavy off the floor generally needs to be dialled back. That's when variations and opposite stance becomes almost mandatory.