I am about to buy a large 24 x 36 inch self healing cutting mat.
The new Olfa mats are 1/16th inch thick while the Birch are 1/8th of an inch thick.
I usually steer clear of Birch products but I bought a smaller 18 x 24 inch Birch mat years ago (at least 6 years) and it is still in great condition. I was prepared to pay for the more expensive Olfa but I now discover that they are now only half the thickness of the old ones.

Would you recommend the new 1/16th of an inch (1.5mm) thick Olfa or the 1/8th of an inch (3mm) thick Birch?

I've never heard of Birch cutting mats.

I got a Riley Blake double thick mat that's printed on both sides. It is so soft, little bits break off all of the time. And my fabric gets pushed down into the cracks and pulls the threads.

I've also used the big white mats, and they are terrible.

I really love my Olfa mats!

Are your Olfa mats the 1/8th of an inch thick ones or the new 1/16th of an inch thick ones?

Sorry haven’t heard of the Birch product either and only found an Aussie site when I googled.
My Olfa mats are all OLD and working well, out of curiosity I measured their thickness and they seem to be 1/16th” of an inch.

I purchased two of these mats back in 2016 and have been very happy with them. The only issue is that the mats are exactly 36" wide, so the grid on the mats only goes up to 35". This actually works better for me, because my cutting table is exactly 36" wide, so a mat that has markings up to 36" will hang off the table just a little bit. I like that the mats are two-sided, so I can flip them over to have a different color if my fabric isn't easily visible against the color on one side.

1/16th or thinner.

I now have a Marte11i mat and it seems to be kinder to my rotary cutter. Previous1y I had an O1fa and it 1asted a 1ong time.

I couldn’t find on google where they were changing to a thinner product, where did you get that info. On this current link olfa describes it as 3.0 = 1/8”
https://www.olfaproducts.com/olfa-rm...tting-mat.html

I have one by Lori Holt/Riley blake and was surprised at how thick/soft it ish. I find myself pushing too hard into it and won't order any more (I have multiple color mats for my vision problems.)
Martelli or Olfa or Fiskers for me.

and if you don't shift/turn your mat around all the time a large one is not costeffective because you won't used 75% of it.

I got creative grids mat it was expensive but seems very nice. It has markings on both sides, one side is supposed to make it easier to use the GE design rulers. (Stripology rulers)