I think I've found a bug in v1.0.10 running on my wrt54g. The forced update is acting in hours, even though Gargoyle shows Days and /etc/ddns_gargoyle.conf shows:-
service ddns_2
enabled 1
service_provider dnsomatic.com
ip_source internet
force_interval 1
force_unit days
check_interval 15
check_unit minutes
force_interval was previously 3 and force_unit days. After being banned by dyndns for abuse, the history at dnsomatic showed 3 hourly polling. Changing to 1 day (as above) via Gargoyle resulted in hourly polling. I guess there's an out-by-one error in the field counter somewhere. As a work-around I can make it 72 "Days" and check the logs in a few days.
Thanks for reporting this! I've found the bug & fixed it in the SVN source repository. The fix will be released with the next version (should be in the next week or so).