I had a engineered hardwood installed on 3/16 inch luan (over plywood subfloor; on-grade with basement underneath). When the installer arrived I called and asked for adhesive recommendations. They replied "Any urethane adhesive", which I relayed to the installer.

The installer seems to have done a good job. There are no squeaks, loose boards, cupping, or other obvious defects. However, the installer left an empty bucket of adhesive in my garage and I discovered that he used Roberts "High Performance Acrylic Urethane Wood Adhesive". Realizing there was probably a difference between urethane and "acrylic urethane". I found my way to this website and am now worried about the future of my floor.
The floors have been in place for approximately 10 days. Again, there are no obvious problems, but how long will I have to wait until I can sleep at night? If the adhesive were to fail, would it occur right away? Should I be worried about the adhesive failing when the seasons change and the humidity rises and falls? Or, does this adhesive have some "elastic" properties because urethane was included in the polymer?

Am I overreacting since the floor is not on concrete and an engineered product was used? Any info or advice would be appreciated. I'm not sure what to do since the floors appear fine and the Roberts product clearly states that it can be used for engineered plank.

BTW - This site is the best place on the web for this type of info. I wish I found out about it earlier.

Thanks in advance.

You'll be OK. Acrylics are perfect for engineered wood. Just don't think about using them for solid wood flooring.

One of the best adhesives for engineered wood, is Taylor 2071. It is a cross-linking acrylic.

I'll second that. Your floors should be fine. They will not fail due to glue failure. So, "Don't worry, be happy."