Hi starfish 9 (and awoods),
It’s not the latex that causes back issues (or any other material for that matter) but the design of a mattress and whether it’s a good match for you or not in terms of PPP. There are hundreds of different latex mattresses and one may be “perfect” for someone while another one may be completely unsuitable for them to sleep on. Any combination of materials or any mattress design can work well for some people and not for others. There is no material that is “better for backs” than another because it always depends on whether the mattress is keeping your spine in neutral alignment in all your sleeping positions although having said that … latex does have an unusual combination of properties that gives it the ability to contour very well (which is important for good support) and it also has a higher compression modulus so that even softer latex can be more “supportive” than other types of foam materials. There is more about what I call primary support and secondary support and their relationship to pressure relief in post #6 here and in post #7 here.
The break in and adjustment period is part of any new mattress purchase that is different from the mattress you are used to sleeping on and would be part of any new mattress purchase … latex or otherwise (see post #3 here). Latex will soften and “break in” less than other types of foam materials.
The most effective way to see whether a mattress is a good “match” for you in terms of PPP is based on your own personal testing or sleeping experience but when you can’t test a mattress in person then the options you have after a purchase to either exchange a mattress or individual layers or return a mattress would normally become a more important part of each person’s personal value equation.
Hopefully some of the other members will see your question and share their experience but I would be very cautious about using anyone else’s experience as an indication of your own because each person can be very different and one person’s experience may be very different from someone else. In general terms though … there are many examples of members that have thought that their mattress wasn’t a good “match” for them at first but after 30 days or so were sleeping very well and this is common throughout the industry with any type of mattress or material.
Phoenix