My X1 took well over a month even to start sounding good, and really 2-3 months before becoming exceptional. I have had it now for about 9 months and, seriously, I'm sure it is still improving. I've never before experienced such a dramatic change from running in of any component I have had, and over such a long time. After the first month I still wanted to sell it, and now I cannot imagine how a digital component could sound better.
I tried the isoacoustic footers with my X1 and I also found that it made the sound worse - sucked out the bass and lower midrange and made it sound thin. I just leave it with the stock footers.
I also prefer the ethernet input to the fibre optic cable, which I find a little artificial sounding. I use an Uptone etherRegen with a DH Labs ethernet cable which I found did make an improvement. And I also prefer native file resolution - no upsampling.