What Bluetooth stylus are you using with your iPad Air 2?
I am using a Bluetooth Adonit Jot Touch with Pixelpoint on a new iPad Pro and it is working just fine and dandy and keeps a connection.
Not sure where your pricepoint or budget is for this.
i am NOT a fan of the smaller iPads for drawing.
The standard size iPads are much better for drawing and drawings apps and the original iPad Air doesn't use the newer screen technology of the iPad Air 2.
BTW, ALL of the stylus makers have finally worked out all of the technical kinks in their stylus lineups so that they work properly with the new screen technology in the newer iPad Air 2 and probably why my Bluetooth Adonit stylus is working fine with my iPad Pro.
It maybe more of an OS issue, now.
What stylus are you using on your Air 2 and how long ago did you purchase this?
Apple is still selling the first generation iPad Air in either 16 or 32 GB configurations which DO NOT USE the latest screen technology of the iPad Air 2.
Apple is no longer selling the iPad Mini 3.
It is either the Mini 4 (which, I believe has the same screen technology as the iPad Air 2 ) or the iPad Mini 2.
Also, you may get more of a discount on any model iPad if you check Apple's refurbished store.
Refurbished Apple are products that have been repaired and reinspected by Apple and are treated just like new product with the same warranty coverages.
http://www.apple.com/shop/browse/home/specialdeals