i'm 24, married, no kids and work part time. i have six girlfriends that i consider my main support system. i have to preface this with i HATE the phone and only two of them are friends with each other.
one of them is in law school and uber busy. i talk with her on the phone maybe once every 2-3 months but we text/email/myspace comment probably once a week. because of ridiculous life circumstances i haven't seen her since march.

she will be home for christmas next week and excited doesn't even begin to cover it.
another is a flight attendant. i never talk to her on the phone or email, but we see each other about once a month when she is in town.
the third is a mother of three kids under 5 who has gone through major life changes this year (ended a 6 year relationship, moved to a new city, working for the first time in 6 years, etc etc). i talk to her through email/myspace/text every day to every other day. we see each other at least once a month.
number 5 is my newest friend. she is the only one that lives in my town. we never talk on the phone except to make plans but we hang out 2ish times a week. being friends with her also opened up a whole new social circle for me, so i have a few other less close but still good friends that i also hang out with about once a week.
the last is a little strange in that we met online when we were 13.....she's one of my oldest, best friends but we've never met in person. she lives on the east coast, i live on the west. we talk on aol once or twice a week and on the phone probably twice a month (we'd talk more if the time difference wasn't so big). we used to email 4 times a week or so, but i've been a slacker in that area lately.
i guess my point is that every friendship and every circumstance is unique. whatever makes you still feel "close" to your friends is normal.
ETA: wow. that was really long. if you read through this whole thing good for you.
