Scheduled nap time for infants

My triplets turn 7 mo. old this Friday. Is it possible to have them on a
nap schedule? (e.g. It's 10 o'clock, time for nap) Currently, I let them
get up in the morning whenever the wake up, unless it's after 9, then I wake
them up. I then put them down throughout the day whenever they display
tiredness. Of course, they are rarely all down at the same time, but the do
usually go to bed at night pretty close together. But even when they take
naps, their duration is different. Ben can sleep for hours, while I
consider myself lucky if Elena sleeps longer than 1/2 hour.

If it's possible, do you have any suggestions on how to accomplish this? Or
is it not worth it until they are older?

--

Gayle
http://www.babiesonline.com/babies/d/datriplets/