I got a latex one from Ikea but at the same time, I bought one of these for a guest room:
https://www.amazon.com/gp/product/B003CT37LA/
The Amazon one was way more comfortable. They sell basically the same mattress at Costco too under slightly different name (but for +$100 or so I think).
Long story short, I've ended up buying more than 5 of those Sleep Innovations mattresses due to relocating (not wearing out). So I'd vote for that. The Ikea one was fine it just was less comfortable as the latex had less give. The Amazon one is still firm but has good amount of give.
Edit: I just noticed it's out of stock with the smooth cover and ridiculously overpriced with the quilted cover. I have seen it go in and out of stock but if you're interested in it, check CamelCamelCamel.com and maybe a new version is coming out.
Sleep Innovations Shiloh 12-inch Memory Foam Mattress, King https://www.amazon.com/dp/B003CT37LA/ref=cm_sw_r_cp_awd_8fhwwbVWV3JHY
Huh. It's even a lightning deal. We bought two doubles in the 10" size as well for the guest rooms. Will not be going back to conventional mattresses. No evidence that they don't last as long and even if they don't I can buy multiples. Great sleep. Really improved ours a lot.
Well, this is the one I purchased. It's a bit more expensive now, but it's been right just shy of 3 years and it's stayed very firm. We got a king size.
Got this mattress and this foundation on Amazon a few years ago. I'm hella happpy with it -- the foundation ended up needing a little bit of reinforcement after a couple of festivious nights, but has held up well and breaks down easily for moving.
The mattress comes vacuum packed. It was unbelievable to me that a king size mattress fit in a box that was a little smaller than two kegs stacked on top of eachother. Both are Prime^^TM eligible.