My friend has used ProSeries for the last 10 years. Each year in January, she rolls over every freaking return. She has about 2K current clients but her system has more than 5K clients. Her employees complain about the slowness of the network and I keep telling her about the extra burden on the network. She says that her "input" employee doesn't know how to roll over returns and that's why she is doing it.
If a client didn't come back the following year, there is a 95% changes that he will not come back in the future. So, I don't roll over any until I have them in front of me.