Its not about the bearings so much, its about the lubricant.
But as long as we’re talking about bearings, here’s a few things:
Smaller factor, but for longevity you’ll want steel bearing cages, not nylon. They tend to hold up better, especially if they’re well made. The best steel cages are riveted, but I’m not sure if there’s even any of the 608 size that do that.
The big factor, You’ll want contact seals. Different companies have different abbreviations for their sheild/seals. But very often metal sheilds are non-contact, and rubber seals tend to be contact seals, but not always.
For Eskate, you don’t care about bearing friction. It won’t slow you down in the slightest. So get full on contact seals.
Ceramic, Don’t bother, especially with Hybrid ceramic.
As it turns out with hybrid ceramics having the ball so much harder than the races only causes the races to get worn by the balls faster, so the performance drops significantly quicker than with normal steel bearings. And full ceramics are just crazy expensive.
And the biggest problem of all is ceramics don’t tend to fail safe, they just asplode.
If you’re going to spend that much money, just get a full set of these:
https://www.amazon.com/NSK-608DDU-Single-Groove-Bearing/dp/B01HBY7OXI
But for the Lubricant, I’ve made a thread on that.
https://forum.esk8.news/t/id-like-to-sell-you-all-on-schaeffer-274-grease-for-eskate
Get this stuff in your bearings, and they’ll be set for a good while.
Zealous already comes with decent grease, so I wouldn’t just rush to get this in and replace it ASAP.
But zealous grease also tends to wash out pretty easily, I’d give them a clean and re-lube after two months, or after riding them in the wet.
But any skate bearings that come with oil I’d just straight upgrade to 274 straight away.