I find my D1x would be probably with me for the next two years, the current issue is with the EN-4 which is now not really perform well at my requirement.
For my photography style, it normally last for about 2 hours (for a half day work) that filled a 1GB MD in RAW image files. My perfect battery for D1x would be the one that can last for 5 hours of continous operations.
I found there is some option in external battery, but instead of this, I would like to see if these is higher capacity battery cell possible for the EN-4 rebuild.
Nikon D1x, Nikon FM3A, Canon S45