Are you building a log cabin of 'real logs' (species?) or with 'log siding'. Any details on the type of log cabin - ranch, overhang, chinking, preservative treatments, finishing, etc. would be helpful.
Log cabins used to be a temporary building that would use the materials at hand in the forest or near a wooded lot. They were not something built for long term housing or where better materials were available. Log cabins were logs stacked and set in a way that when some of the lower logs decayed, the cabin was jacked up, and a new log set in to replace the old. Nowadays, some log cabins are built with the logs bolted and held in place with rods and the like, with electricals in the walls that make replacing a log a near impossibility.
I witnessed a log cabin ($300,000 to build in the middle 80's) assembled out of logs that were likely over-mature trees that possibly had already begun to decay. Within 10 years, half of the logs were in advanced stages of decay and the verdict was it was a total loss as there was no way to make repairs.
There are 'stories' of log cabins lasting for years and years. But not much documentation that new logs were not added to replace the decayed logs. Most wood decays unless kept quite dry.