I was that parent who had one in daycare and was having our second ~ we loved our provider so much that we paid full pop for our older daughter although she only came a few hrs every other day for social time and time for our new little one and me to spend just us time. Our provider also had an opening for when I was going to back opening up for our second for when I was due to go back to work. Timing worked out great.
As a provider I wouldn't hold a spot open for a year ~ that is alot of income to miss out on. I agree with playfelt that if your holding a spot you could lose another chance with a great family that would be interested.