Most of the Duracell 9v batteries have about 560 mAh. 150% more capacity sounds pretty good… May be the way to go, although the most comfortable option, may not be the cheapest one on the long run. (about $8 each when a mighty max will last 3-5 years and it will cost $21).
I guess, like most of everything, it comes to preferences and the good thing is that either way you can always have a plan B if the battery dies at the wrong moment.
Thank you all for helping me understand the basics of this set-up!
I wish you twice as much of whatever you wish for me. : )