I’m A330, but that sounds very similar to what happens with us. In my experience, if you let DPO do its thing, every descent will have the thrust coming up at one point and speed brake being used at another. That defeats the purpose of minimising fuel burn. I believe it’s because the forecast winds loaded into the FM are different to the actual winds. What I do, is if I see that thrust or drag is needed to maintain speed on the latched path, is pull Open Descent. i.e. the aircraft is now pitching for speed (not path) and thrust remains at idle. Usually, the above and below path errors will average out and once below the stronger upper winds (and before any STAR altitude restrictions) I’ll update the FM calculated path (re-enter Vapp) and reengage managed DES. I’m usually back to being very near the path and speed brake/thrust requirements thereafter are minimal.