For the record, he did so at the age of 67, facing both failing health and the loss of that which he seemed value most (his ability to write). While you can argue (with no small amount of validity) that his life choices contributed to this decline, his decision to take leave of life seems consistent with his views expressed herein on being true to oneself and one's calling, and he does seem to have fit plenty of life into those 67 years...

This quotation seems pretty apt and in my view makes his suicide seem reasonable and consistent with his views:

"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming “Wow! What a Ride!" - Hunter S. Thompson