when to replace front wheel bearings on a 4x4

[Eman85]

Even though your wheel bearings are not making noise and your truck hasn't seen any harsh conditions, age is still a factor. Bearings are exposed to a lot of stress, weather, and vibrations even in normal driving, and over time, the grease inside can break down, causing wear. While 90,000 miles is relatively low, the fact that they are original and 26 years old means that some of the materials (such as the seals or grease) could have degraded, potentially causing future issues.

And the future issue would be??? The only issue would be you would need to replace them when they wear out and make noise or have excessive play. As I said before replace them now and you'll be replacing them often as what you purchase will be worse than the 25yo ones with 100k mi. on them.