How about you shoot for 200+ watts and progress from there? Personally, I've just watched the number and compared it to my perceived effort after my rides.

For instance, here's a ~33 mile ride I felt like I put in a good effort on from beginning to end: https://www.strava.com/activities/928617959/analysis

I had a 206W average, according to Strava. So, for me, that's pretty good. Now, of course, if the ride were 1/3rd as far, I could have probably gone harder..

Typically, however, folks are looking to hold a certain wattage for a given length of TIME, not distance. Given the variables involved with terrain and whatnot, it tends to be a more reliable measuring stick.