I update my CV once a year so it is usually up-to-date. I don't update it so that I can look for jobs, but just to keep it updated and the presentation refreshed. I think it is a good practice to review your achievements and list them every so often - helpful in appraisals!
That said, I am not very happy with my CV. It lists all my important achiements, but I think it could do with some pzazz (highly technical word

) injected into it. I don't think my CV is in too bad shape, though, because I wouldn't have got the job I am in if it were poorly present, but I would love for someone to read through and give me advice on any improvements.
Raindance