If you’re doing a renewal of licenses then the number of licenses you purchase needs to match the number of devices. A renewal effectively replaces your existing licenses with exactly what is on the order. If you add additional licenses then you get another device license, but the co-term date is adjusted as the license ‘flows’ across all devices in the organisation.
For your two access points, yes, you need to purchase two licenses. No, you can’t purchase one 5 year one, there is no way to split it.