This is a good question. Why bother to merge multiple reservations at all?
To answer your question, Steve:
If you didn't alert the CM checking you in on day 1 as to your multiple reservations, then yes, you would be assigned a likely different site number for your subsequent reservations. The chances of you getting the same site are small (statisticly speaking). And if you alert the CM on day 1, you're relying on the CM to do their job right so you don't have to come up to the office each time a new reservation starts or use the online method each time.
You also have multiple reservations and multiple magic bands to deny on your reservations (since you only need one). We bring the ones we paid for (nice designs) that work well for us.
Making ADRs at the 180+10 window has a bearing based on your arrival date. If you're willing to wait till sooner to make ADRs all the way up to the day before you dine, you can take whatever is available. I like to throw some reservations out there just in case. Our park touring pattern is pretty predictable and I have nearly always kept what I booked way out. This is good especially with hard-to-get dining choices. But the choice is up to us to make.
For an investment of 10-15 minutes at a time well in advance of my choosing, I can get things boiled down to one reservation number. The simpler the better, I say. They move any deposits (the money is the real issue/work in doing this) and build out the full range of dates.
So yes, doing nothing and living with multiple reservations CAN be okay but there is margin for error and issues. That's an option - but I'd rather eliminate the margin for error to keep things simple.
I do it for peace of mind, basically.
The choice is, like I said, up to each one of us to make.
Bama Ed