My Voron V2.4 contains two dozen F695 flanged bearings. I found that some failed after less than a year, simply because they had run dry. It seems that many economy bearings come with a very low amount of grease inside and will run dry pretty fast.
Bearings like these should get enough grease to fill at least half the air inside, even more is possible because they will get nowhere near their specced temperature limit, so the grease won't spill from overpressure.
This tool makes it easy to repack bearings. It also allows to flush old grease out simply by applying enough grease that some of it spill out of the relieve slots on the top part (see picture). You need a standard syringe filled with just a few drops of grease for this.
If you change the type of grease in a bearing (you don't know what the manufacturer used, btw), flushing is advised because different greases can be incompatible and degrade into a rubbery waste.
To refill a bearing, follow these steps:
If you have trouble filling a syringe with grease, there is a very good and short demonstration in this Youtube video:
The author marked this model as their own original creation.