We got a free (used) Rainbow last summer. It was 13 years old. Hubby had to replace a few boards due to insect/animal damage, but the thing is solid. It is giant one, so adults can even swing on it. Their 13 year old daughter still used the swing. Rainbows are expensive, but this baby is going to get 20plus years of use with no problem.
I did a lot of research last summer. We were close to buying the Costco or Menards kind but I am so thankful we waited for a truly quality set to come our way (we spent 2k on rubber mulch and extras, so it was one expensive free set!).