Ed try a search on sealed bearings or Alko etc etc .
I use em and normally get a year out of each pair BUT don't take any chances if you think the bearing is on it's way out.
They have to be properly maintained . ( Pressed out with a fly press or something similar , and replaced with copious amounts of decent quality marine grease . There is also a theoretical limit on how many times you can press new bearings into any one hub but I don't lose too much sleep over this )
There has even been a suggestion that you can split , inspect and re-grease sealed bearings but I don't believe anyone actually does that , other than in a short trip emergency
If I were starting off from scratch , I would probably go with taper bearings that are easy to properly service and re-grease , but you pays your money and takes your choice !
ALWAYS let your wheels/hubs/bearings cool right down after any trip before you launch or recover.