My experience with a built in GPS (ASUS R2h) left me cold to even considering that approach again. It would generally survive a couple of hours standby though and I don't think it is powered in that state.
The R2h could take 3-4 minutes to get to lock from a cold start though. What is the cold start performance of your Viliv GPS? It shouldn't be too bad. My Garmin 5000 PND (no internal battery) requires less than a minute 95% of the time.
Yes, it takes about 3-4 minutes to get a lock from cold start, too. But I don't blame that on the Viliv because that was my experience with a laptop, also.
I have had the Viliv about a year now and I really love it. For one thing, as it is so much easier to deal with than the laptop with a USB-ed GPS was, I use it a lot more. It powers up and down quite quickly, although I am thinking about replacing the pre-installed Win XP with Win 7 to be even quicker along with other Win 7 benefits.