I don't think sleep mode vs. full start have any difference considering the aging of the machine.
AFAIK, the old thinking that starts wear down the PC is based on the actual fysical things that take place - HDDs speeding up from stand still and warming up etc.
When a machine has reached the end of its life span, the final failure usually takes places at that very moment of the biggest strain, and so people think it's the starting that causes the failure.
Those very same things happen when you wake it up from sleep mode (assuming you have HDDs :o) The only difference would be not needing to reload memory and start software, which in itself doesn't matter. With an SSD
there are practically no moving parts that could be affected By daily restarts, I assume.
I've had so many problems with sleep mode, not only with SONAR, that I quit using it long ago. I think there are even differences between PC:s.