A rent increase of 10% or higher would need a 60 day notice. My guess is the owner may be considering it is under market and attempting to catch up to the market. A quick rental survey would be in order. You can do this my checking local paper or online version or craigslist to see if your rent is in order.
Your rent increase is an increase of 8%. When is the last time yoiur rent was increased? If you compare this to the average rate of inflation (about 2.5%) this seems high. But because of all of the foreclusures on the market, folks are losing their homes and being forced into the rental market. This creates a higher demand...which means higher rents. Check craislist or your local newspaper....what would it cost you to rent the same apartment today? You MAY still be getting a eal!