I don't do 2 pet battles because my battle pet isn't up for it. She'd be crushed, and I'd be quite sad to get her hurt.
I tend to do the ones like Boochi or the defender robot from Kreludor (forgetting his name atm) that I can battle on hard and take out in one round with lens flare, though after I've won my daily np limit, occasionally I'll move to another one that has low enough HP that I can do them in one round for items and just general variety.