Depends how fast you are injecting packets but seems quite a wait. Take for example, you should need about 50,000 ivs. The N900 should easily be able to inject about 200 packets per second. so
50000 / 200 = 250
250 / 60 = 4.16 mins
This is without any traffic been generated by clients already attatched to the AP.
This also depends on a few things, Proximity to AP, dropped packets, disauthentification notices and processes running in the background.
Try getting closer to the AP fo starters then make sure you have loaded the bleeding edge drivers properly.