There is a lot of natural variance in circadian rhythms. Mine is also much longer than 24 hours. If I let myself go "free-running" then my sleep/wake patterns cycle around 24 hours about once a month. The lengthened cycle is not necessarily unhealthy but it makes it very difficult to conform to a 24-hour schedule. If you have continued difficulty with your sleep cycle then talking to a doctor specializing in sleep disorders might be a good idea. There are a variety of options for dealing with the issue.