I use cheap batteries from the dollar store and I definitely ran my vintages for much longer than 2 generations/runs. I'm not sure how long they last but probably 4-5 continuous runs with the best character. Oddly enough, when the power gets really low in the batteries, the display will turn off and only reappear during an animation or when the buttons are pressed. Thus, you can effectively run it to exhaustion. If you wanted to be extra stingy, you could try to reduce how often you press the buttons as pressing the buttons and using icons depletes much more power than the idle display.
I'm not familiar with Varta batteries but if it's generally considered a heavy duty, reliable brand, you probably have the best shot at longer battery life. With the exception of the Osutchi and Mesutchi, there isn't really any need to keep a vintage alive past one run as there is no continuity, unlike the newer versions.