I have Thunderbird on a USB drive for travel. Running Thunderbird I also have it on my desktop. We have 5 calendars Thunderbird is keeping track of. My issue arises if I don't synchronize the USB Thunderbird for a few weeks. It doesn't just synchronize what is new, it acts as if it has never synced before. I end up with 35,000 entries being synced before I can use the program. Doesn't happen if I use the USB calendar every few days. Is there a setting I'm missing that makes Thunderbird resync every calendar entry if not used within a certain amount of time? Is there a setting so it will only sync the past 30 days and all future events? Thanks in advance