For me it depends on how sedentary I am when off the bike. If I'm laying around the house and driving instead of commuting the decline can come pretty quickly: maybe 2 weeks or so.
If I'm moderately active (jogging, weight room, etc) a couple of times a week it can take a few months.
It's really going to vary from one person to the next but 10 days shouldn't do much unless you're completely inactive and/or drinking heavily.