Hi cinn,
You can see some of their past return policies if you go to the wayback machine here. At different points that I can see on June, 2013 there was a 30 day free return policy here, and on Dec, 2013 a 30 day exchange policy here (no returns or refunds), and on August, 2014 a 30 day policy here where you had a choice to return the mattress and pay for return shipping or exchange it for a different one for free and on Oct, 2014 40 day return policy here (which I believe was current at the time this post was written) and you can see in post #2 here that at one point they also had the option to pay an additional $29.95 if you wanted a return option when you purchased the mattress.
ADDED: Since this time they have also had a 40 day exchange policy here (exchange only) and a 50 day return policy here and Since Dec, 30th, 2015 until now (Jan 10th, 2016) they have had a 50 day exchange policy.
I don’t remember them having a 90 day trial but of course it’s possible they did at some point and I just don’t remember and it wasn’t captured by the wayback machine.
Christeli is one of the options in in post #12 here which includes the better online memory foam options I’m aware of but some of the others have longer trial periods so you may be thinking about a different company.
Phoenix