I also putt at home on the carpet. I used to use headphones as my target cup, but now I have a cheap plastic putting cup.

I use the time more to work on aim and my stroke as opposed to focusing on accuracy in terms of distance. Greens are so varied from course to course (and day to day, with weather and upkeep, etc.) that I just don't worry too much about it.

Before every round I spend as much time as I can putting on a practice green to calibrate myself to those particular greens. At home, I still try to get 100% of 'em into the cup, but it's not my top priority.

That said, I'd appreciate some other answers to this question - maybe I'm missing out on something?