The Trail Ridge Road is not guaranteed open at any time. I have found it closed by weather, in August, July, and September. In fact, it was not until my fifth attempt, in 2009, that I finally got to drive it. At those extreme altitudes, no one can guarantee when it will be open.
In 2001 the NP staff advised me to take CO7 to I-70. And I have to say, it was a magnificent trip. Nothing like the Trail Ridge Road, but full of its own attractions.
Lifey