The sooner the better IMO. I was trying to save some money and sign lease last minute but my lady turned me around with reason. You need to move in at least a few weeks early, figure out how noisy the neighbors are at night, get acclimated to the higher altitude (some it's not a problem, others like myself it was headaches and lightheaded when doing more than a walk. Lasted a month), learn where grocery store is etc....
Talking with some of the second years during interview, they said it's possible to live +30 minutes away as others did and it worked, but the closer the better. I made a 20 minute drive rule and stuck to that (got a place in downtown littleton next to lightrail stop).
If you haven't noticed already, prices here are expensive so be cognizant of that. Find an environment for success but don't break the bank. Looking at my spreadsheet I made on loans, if we get the 6.8% interest loans by end of 4th year $1,000 becomes 1,300.19. and that doesn't include the length of your residency and if you will be paying it back during that time or just forbearing it. So, every penny saved counts.
I am a local here (as of 3 years ago) so go ahead and ask any other questions you might have.
