You may find that the filter element cost is not an issue. Where I used to work all of the Refer unit diesel generators had similar CAV glass bowel type with a filter element about the size of about 4" tall by 3.5" wide water seperators and in the 3 years that I worked there I never had the element plug up on any of them (I believe they are 30 micron elements). As long as you drain the bowel of the gunk or water the filter element will last a long time. This assumes you have no abnormal tank or fuel issues.
If you are curious about the micron ratings you might be able to find them at these sites:
http://www.wixfilters.com/filterlookup/index.asp
http://www.filtermart.com/fpdbdb/fmccross.asp
http://catalog.baldwinfilter.com/
Wix most often give the micron ratings; the others only sometimes.