Your cycling fitness is not going to deteriorate over the course of a ten-day vacation. Afterwards, you might feel a bit stale or sluggish for the first couple of days on the bike, but that has more to do with the dehydration and stiffness that typically accompanies travel.
By taking two rides to get back in the swing of things, you will be ready for a high-quality, effective training session on your third ride back. This is the first workout that should include hard intervals. When athletes try to jump back into their training programs the first day back, they tend to exercise harder or longer than normal, figuring they have to make up for lost time. This sometimes ends up causing more harm than good, because the spike in fatigue means you're tired for subsequent workouts, which in turn means those workouts are less effective.
For people who are taking shorter, more frequent business trips, a single recovery ride the day you return, or the following day, should suffice to transition you back into your normal training program.