I own both the D810 and the D750, and I'd say it's a matter of horses for courses. I mostly use the D810 as a studio camera. Image quality is awesome, and the size and weight are not a problem. The D750 for me is more for general use. It's more feature friendly, and as others have said, parallels the D7200 in its features and controls. Both cameras can be rented for hands-on experience, which might be an option to consider. The smaller file size of the D750 is a benefit on older computers. Objectively speaking, I would say the D810 is the superior camera, but I tend to use the D750 more. I hope some of this helps.

I get one of those each time I have my Avalon dealer-serviced. Everything is conscientiously checked off, all tires, even the spare. I've had to dig out that spare when the pressure warning system lit up, and it was no easy chore. I promise you no mechanic has set eyes on it.

As to oil changes, I'm old school. I have it done twice a year, spring and fall, regardless of mileage.

It's Dollywood, no E in the middle. [grin]

Got an email that Nikon Service has shipped my D750 today. That's less than 10 days turnaround time.

I share very little unless unless I'm shooting portraits. A lot of my photography is more about exploring technique or problem-solving -- how best to make the shot or get the effect.

70 years old. Took up photography after I retired. I've been more interested in building a basic skill set than in playing with the gadgets. That being said, I appreciate the array of features my cameras and other equipment offer. There's always something new for me to learn, and it's fun to see how the more experienced use what I may not. I will never test the limits of what the equipment can do, but others have different needs and applications. I'm happy the technology can serve so many and such diverse needs.

And I don't do video -- yet. Seldom explore the upper regions of the ISO -- yet. Probably look like a newbie much of the time. But I'm having a ball in the process.

I sent my D750 in for the recall service today. I'll report back when I hear anything from Nikon.
My experience with Nikon recalls (and I have a lot of experience) is that they provide quick turnaround . . . if they have the parts on hand.

Roger Cicala published a test article last month on the problem with cheap filters.

https://www.lensrentals.com/blog/2017/05/yet-another-post-about-my-issues-with-uv-filters/

I've bought two Nikon D7200s, refurbished by Nikon, from Adorama in the last 12 month. Had no problems with either.
They have a 30-day, no-questions-asked return policy.

That's been my observation as well. I would expect another round of promotions during the Christmas season.

I tried doing that once. It was the longest 4 hours of my life.

Sorry to hear you're having equipment problems. I own the Tamron 70-300mm, and it's been trouble-free in my experience.
Tamron's Support website has detailed instructions for requesting warranty service. You might like to check that out.

http://www.tamron-usa.com/support/

And you can find a copy of their warranty statement as well.

http://www.tamron-usa.com/support/warranty_statement.pdf

I can identify. My own cure is called "regret."
Made enough mistakes buying expensive gear to be much slower with the plastic.
I also rent things I'm curious about, quick relief from GAS.

This is the crux of the matter for me. I own a lot of glass. Much of it I seldom use, but every time I think about selling something, I dig it out, slap in on a camera, and rediscover the reasons I kept it. I've even bought back lenses I later regretted selling. Every lens has its own charm, it's own magic. I don't think you can go wrong with either of the two lenses. I have them both, and I can't imagine letting either go.