"Loading addressbook summary" very slow with cached online addressbook

I've got a CardDAV addressbook stored in the free 'fruux' service and I've set up Evolution to use it to store my addresses. But it's very slow when writing emails. If I write the person's name in the 'to' box, it's very slow to recognise the name and add an underline to indicate it's been recognised. If I click the 'to' button and attempt to search for a name, the bottom of the dialog shows "Loading address book summary" and it takes 10-20 seconds until the my search result appears.

I'm using a slow (3G phone) internet connection, but I have the address book set with "copy book content locally for offline operation". However, it appears that when I'm on a *slow* connection, it ignores the local copy and keeps using the online copy regardless.

Is there some way that this situation could be improved, so that the online content is only synchronised periodically, and not every time I add an email address to a new email?

I'm using latest Evolution 3.2.3 on Ubuntu 12.04 LTS.