For 1 hour/day I would have cancelled the sub's years ago.
What new features would you be using?
What features have been added in recent years that you have made good use of?
How many times have you used support?
However, make sure you make full downloads for each SP while the subscription is still valid.
Actually we had it cancelled, but it is like Anna just mentioned. Some of our customers started sending us 2011 files and we needed to do some work to them within SW for them. So it seemed best that to be able to work with our clients we need to stay current. So I guess shortly I may have to upgrade to open their files anyway.
You don't have to make an either/or decision. Multiple versions can be installed on one machine. If you have the luxury of separate machines, then so much the better.
To add to what Kelvin asks....
Do you regularly get customer data, that is the latest SolidWorks version, that you must be able to open?
What I do is test the new version of SolidWorks on a copy of of production data first before deciding when we upgrade. I want to make sure there is not a bug that would leave us dead in the water. If testing goes well we upgrade. It is important for us to be using the latest version of SolidWorks as many of our customers are using the latest and greatest.