I was wondering how well SPM's coregistration performs when BOLD data from a subject from different sessions are coregistered to T1 data e.g. recorded only in the first sessions? 

In other words, when scanning subjects, sometimes the session has to be interrupted and the subject is taken out of the scanner and back in. Normally, after returning to the scanner, another T1 scan is performed and used for coregistration to the BOLD data from the same session. 

However, is it possible to just record a T1 scan (e.g. in the first session) once and then coregister BOLD images from several session (e.g. 3 sessions each on a different day) to this single T1 scan? 

greetings

David