I switched last year to UniFi access points at my clinics over the Airport Extreme. I am about to sell my 2 802.11ac Airport Extremes and go with 2 of these
https://store.ubnt.com/unifi/unifi-ap-pro.html . You can mount them to the ceiling and get even better coverage, the pricing is right there with the extreme but you get much more robust settings and control over your network.
If you still need the router function of the AEBS then I'd say stay with it as long as you want but for those similar to me, I already have a good router in place and the AEBS mainly handles my WiFi. These new UniFi AP's are a better way to go IMO.
I like the AP AC Pro line personally but they have a line of AC products from one extreme to other for the most part. So from basic 802.11ac implementation to full on 3xMIMO, guest networks, 1300MBPS, etc. The software to controller the AP's is also fairly nice, simple to used and has many many features as you would expect an enterprise type product to have.
or here
http://www.balticnetworks.com/manufacturers/ubiquiti/unifi.html