I check mine with regularity. IMO the best way to do it is disassemble the linkage and spin the bearing, if they are gritty, or especially notchy or seized, then something needs to be done.
If it's only minor, you can remove the bearing seal and flush them with a degreaser or rubbing alcohol, let them dry, then re-pack with some type of grease. I usually use a marine trailer bearing grease. If the grease is too thick, then it won't distribute properly in a pivot and will result in it seizing again. If it's too thin, then protection is minimal and it'll wash or wear out. As an example, Polylube is too thin and doesn't work very well, but Red N Tacky is too thick. While I haven't used it, the Park high performance grease seems like a good option, so is Phil Wood.
If it's major, where the bearing is notchy, has play, or is to totally seized, then it needs replaced. Keep in mind that replacing a broken bearing is very difficult on some bikes, so you risk damage to your frame. I'd default to replacement whenever practical.
Keep in mind seized bearings will rotated on the axles and inserts, so prolonged use of seized bearings will result in silvering or wear on the axles that will require replacement.
To prevent your issue, I regularly pull the pivot axles out and re-grease the axles, especially on bikes where they are exposed more like Transition bikes. Use the same grease as you'd pack the bearings with, loctite the threads, and grease everything but the threads (axle surfaces, collet heads, bolt heads, etc). The tapered washers you see in a lot of linkages in particular are really important to grease, as they could get stuck otherwise.
In order of bearing durability, it's hard to lay out because a lot of brands use the same linkage design but with differences in implementation. I've found most VPP bikes (Santa Cruz, Intense) to have the best durability and longevity of the bearings/axles. They use dust covers and the bearings are mostly out of the way, along with most of them being in links. The Horst bikes are a mixed bag, Transition's bearing life is awful, but Specialized seems pretty decent because of some rubber seals over the bearings. I've looked at Norco, theirs seem better recessed and out of the way, but not as well sealed. The new Transition bikes have the bearings further encapsulated in the frame and covered by seals.
Typically, I look at the amount of exposure the bearing has (If I can see the face of the bearing seal, it's excessively exposed; this determines how much crap the bearing will pick up), if they are protected by some sort of cover (determines how likely the bearing is to hold grit and run it past the bearing seal), how many blind bearings exist in the frame (blind bearings are a pain to remove), and how many bearings are in links vs the frame (bearings in links are easier/safer to replace).
March 11, 2020, 1:04 p.m. - Shinook
I check mine with regularity. IMO the best way to do it is disassemble the linkage and spin the bearing, if they are gritty, or especially notchy or seized, then something needs to be done. If it's only minor, you can remove the bearing seal and flush them with a degreaser or rubbing alcohol, let them dry, then re-pack with some type of grease. I usually use a marine trailer bearing grease. If the grease is too thick, then it won't distribute properly in a pivot and will result in it seizing again. If it's too thin, then protection is minimal and it'll wash or wear out. As an example, Polylube is too thin and doesn't work very well, but Red N Tacky is too thick. While I haven't used it, the Park high performance grease seems like a good option, so is Phil Wood. If it's major, where the bearing is notchy, has play, or is to totally seized, then it needs replaced. Keep in mind that replacing a broken bearing is very difficult on some bikes, so you risk damage to your frame. I'd default to replacement whenever practical. Keep in mind seized bearings will rotated on the axles and inserts, so prolonged use of seized bearings will result in silvering or wear on the axles that will require replacement. To prevent your issue, I regularly pull the pivot axles out and re-grease the axles, especially on bikes where they are exposed more like Transition bikes. Use the same grease as you'd pack the bearings with, loctite the threads, and grease everything but the threads (axle surfaces, collet heads, bolt heads, etc). The tapered washers you see in a lot of linkages in particular are really important to grease, as they could get stuck otherwise. In order of bearing durability, it's hard to lay out because a lot of brands use the same linkage design but with differences in implementation. I've found most VPP bikes (Santa Cruz, Intense) to have the best durability and longevity of the bearings/axles. They use dust covers and the bearings are mostly out of the way, along with most of them being in links. The Horst bikes are a mixed bag, Transition's bearing life is awful, but Specialized seems pretty decent because of some rubber seals over the bearings. I've looked at Norco, theirs seem better recessed and out of the way, but not as well sealed. The new Transition bikes have the bearings further encapsulated in the frame and covered by seals. Typically, I look at the amount of exposure the bearing has (If I can see the face of the bearing seal, it's excessively exposed; this determines how much crap the bearing will pick up), if they are protected by some sort of cover (determines how likely the bearing is to hold grit and run it past the bearing seal), how many blind bearings exist in the frame (blind bearings are a pain to remove), and how many bearings are in links vs the frame (bearings in links are easier/safer to replace).