Hi, it would be super useful to see an overview of all the slots that you own, and especially the slots you own but that you're not using so that I can schedule flights in those slots. Also, I realized that when I close a route and DON'T release them back to the public, I still have to buy the slot again...
On the airport slots page you'll see some time periods, eg Tuesday 13:00-13:59 that have an asterisk next to them. This means your airine has an unused paid for slot in that time period.
Slots do expire if not used, you normally get many many emails warning you of this. In which case you would need to buy the slot again. It's all in the documentation.
Simon