Congratulations on your first 200K!! (Yup, I said "first". Most people come back for more, despite protestations... )

I rode two permanents when I was visiting family in AZ in 2010. The Arivaca 200K and the Mt Lemmon 100K hill climb. Especially on the Arivaca route, there were certainly some soul-sucking long monotonous stretches of scruffy desert and not a whole lot else. But I enjoyed the ride nonetheless, as the scenery was so different than what we get in the Pacific Northwest. I never got tired of looking at the Saguaro.

Don't bump up to the 300K until you are well and truly ready, regardless of what DH does. Riding at night, after a long day in the saddle, is definitely not for everyone. Get in a few more 200Ks first, build your confidence, experiment with some lighting systems on an easy evening ride (will help work out the kinks) ,etc.

And, again, CONGRATS! It's a huge accomplishment to ride a distance like that. You'll never forget your "first time".

Susan