[Blind-sysadmins] ssl certificate question

Hello, I've got to secure some services using an ssl certificate. Each is operated on a different subdomain for example: www.domain.com pop.domain.com smtp.domain.com svn.domain.com etc. It's now time to renew the certificates, I wasn't the one who purchased the original batch, but the client has a separate certificate purchased at the same time for each service. I'm wondering if it wouldn't be better to do a wildcard certificate such as: domain.com or: *.domain.com in the cert's commonname field? I'd prefer to only use one certificate for all services if possible and it also saves a considerable amount of money. Thanks. Dave.