Getting the shields off isn’t the problem, it is getting them back on that is usually a fail. How old are the bearings? I’d not expect bearings to last much more than a solid season if you have a dusty track.
I’ve used a lot of the cleaning tricks, but in the end, I just throw them out and buy new ones. That, or just put up with grinding sounds until the bearings are just too loose to use anymore.
I’ve found that the key to keeping bearings longer is to do nothing as much as you can.. By that I mean don’t ever use cleaning products to ‘clean’ them out. Just wipe them off so you don’t break down the existing bearing grease.