The manual likely specifies 30WT for 60*F or higher, or 10W-30 for temperatures below that. I personally would change the oil out after 2 or 3 uses. If it's the GCV190 and not the GSV190, it has an aluminum cylinder bore, and you'll see a lot of metal in the oil after a few uses. It will eventually clear up and stay very clean. The GSV190 has a steel cylinder liner and probably wouldn't dirty the oil as much on the first few initial uses.
I have a GCV160 that was broken in with the included 30WT oil and changed after (2) hour-long uses. Then I changed it again after another (2) hour-long uses. After that, it would stay looking clean for 6 months. Lately, I just change it once a season. My engine is from 2004, so it has some "miles" on it.