How long does it take for unis to give offers?

[peanuts]

So I applied for a Bachelor's in Psychology to the Universities of Maastricht and Twente in the Netherlands back in February, and I got an offer almost instantly from Twente, but now a month and a half later still no offer from Maastricht. I don't want to seem impatient, but I'd just like to have received all my offers or rejections before my final exams in May so I don't have to keep thinking about it and can concentrate on studying.
I'm just wondering from any of you who have applied to Maastricht or the Netherlands in general, how long did it take them to give an offer? I've also heard that sometimes you have to apply using the actual final grades you get in July for them to give you an offer (which seems kind of late?) That would probably be too late for me since July is when I'd be actually going to the Netherlands to find apartments and all that.

Thanks!

[Mandingo]

University of Groningen gave me a conditional offer overnight, Vrije Amsterdam however took almost 2 months to get back at me.

From the registration guide I have been given by Groningen, I believe that they will issue an official statement of enrollment (you are now really in) after you mail them a copy of the IB diploma by post. 

Luckily, I had the opportunity to discuss this very issue with a representative because the IB diploma is issued in July. They told me that in cases by which a conditionally-admitted student can not provide proofs that would fulfill the condition of their offer before June or something like that, we would have to coordinate with the IB school you're currently attending and ask them to either provide some sort of statement or ask them to authorize the university so that they can check your IB results online.

Nonetheless, you will still have to mail them a hard copy once the diploma has been issued.