What is a reasonable reimbursement time for conference travel from a department?

In my job before grad school, I could expense items as soon as I had a receipt and I knew exactly when the money would arrive (typically the following pay cycle). In grad school, it seems to be a mystery when I will receive reimbursement.

• I bought tickets and airfare on day 1 of this scenario


• I was not allowed to request reimbursement until 6 weeks later, after the conference


• The conference ended, I requested reimbursement. 6 weeks later, still nothing!

So for the last 12 weeks, my account is down airfare and tickets, and for the last 6 weeks, I'm down the hotel, transportation, and meal costs. I've sent all the emails I can and have asked around -- the response I get is "The finance department does not give exact days of deposit."

Is this the norm in academic institutions? What is a reasonable reimbursement time for conference travel from a department?