Google Voice notification...is there any lag?

i had google voice for a week or so. I had it set up to transcribe my voicemails and text me. It seemed to take up to 30 minutes sometime to get a voicemail from a missed call. Normally this wouldn't bother me, but when on call for work i only have 20 minutes from the time they start calling to answer a call and accept it. When in low reception areas where it wouldnt ring but i would get voicemails it almost caused me to miss a call so i got rid of it.