Front axle seal - how deep?

After replacing the driver side half shaft (2008 Tacoma) last weekend I found the axle seal was leaking on Wednesday. Replaced it Thursday night, and headed from Omaha, NE to Casper, WY. I discovered that I had torn it on installation.

150 miles into the trip it was leaking. Paid a shop to replace it - the one they pulled out had failed with a split around the surface that seals against the shaft.

That one is leaking now, too. The two possibilities I can see are a bad shaft, or that I over drove the seal. I've seen some references online that suggest it should only be flush with the outside of the bore. I drove it until it bottomed out. I don't know how deeply the shop drove the current one in.

I need to drive back to Omaha from Casper tomorrow. I have another seal, and may be able to scrounge enough tools to tear it apart tonight, but I don't want to make the same mistake again.

Any ideas?

/rl