I think these things depend on situations.
I've been a bit frustrated that several people who asked me to keep in touch over the summer were responding to e-mails, phone calls, etc. for a while, but now have quit (and I've kind of hit a limit where I say, okay, I've e-mailed them x number of times now, so forget it). However, most of these people are in education, so I may just wait until August.
I did see a guy friend of mine whom I don't see very often any more on the 4th, who'll soon be moving out to SF.
Another guy friend of mine I haven't heard from since February 1st, but I've been told he's been working multiple jobs for a while now, to be able to continue to afford his mortgage.
What's ironic is that one gal friend of mine DID want to hang out with me last night, but SHE spent 2 1/2 hours on the phone chatting with her other friends, so she didn't get back to me until today.
I guess something is to be said for timing...