OP: If you are regularly opening the hubs anyway, you should be replacing the bearings (use grade 25 bearings in the appropriate sizes) and use high-quality grease. If you ride in the rain a lot, use marine grease. I pack my hubs with LOTS of grease, and let the excess ooze out through the seals. More grease = less room for anything else to get in there.
Also, are you really cleaning everything thoroughly, using degreaser or at least isopropyl alcohol?
And yeah, replace those seals.
If you don't like the maintenance, then yes, cartridge bearings can basically be run maintenance-free until they get rough, which will take a long time. But it's probably not worth buying a new wheelset, in my opinion.