I'm presuming the problem is front wheel bearings. The most common reason
for premature wear is dirt getting in. This happens when the (surely new)
oil seals can't do their job adequately because the sealing surface on the
CD axle stub is worn or grooved.

Second reason is inadequate cleaning of the knuckle inside, such that the
bearing outer does not exactly sit flat. This creates a distorted bearing
that will wear quickly.

Third reason is that the knuckle itslef gets slightly distorted when the old
bearing is pushed out,  See above.

Last reason is inadequate lubrication. Some bearings are prepacked, others
need cleaning and packing with the correct hiogh temp grease.

Stewart DIBBS
www.vysor.com/lancerproject