Reasonable Time-frame to hear back from parents?

[Inspired by Reggio]

Does anyone ever followup within the week (if you haven't heard back right away) and say you'd like to offer them the spot if you really liked the family? Or does that seem too desperate?

Personally I do not chase clients ~ I want people here in my program who value me and are excited to be coming here! So after an interview I tpyically send them a follow up email or or note thanking them for the interview and reminding them that I will be making a decision by X date and look forward to hearing from them again' .... if I DO NOT hear from them again before X date to let me know they are interested and hope I will consider them for the spot as well than I assume they are not interested and when I am making MY finally choice I choose from those who've kept in contact and show keen interest in being here and than when X date comes for that final round of interviewing I will send out a final 'thank you for your interest in the program at this time I am going another route' email and if need be keep advertizing if no one was suitable or fill the space from the remaining options!