I just looked around the Google calendar app and don't see a setting to how far back the calendar will go. I just looked a year back on my calendar and don't see any events but I'm new to the TB too, the only past events it synced were ones that were repeating weekly. I don't think there is a way to sync past events using Google. You could try it using facebook or another type of calendar that you could view from your phone. Another way if you could save those events on a pdf or word file and then store it on your sdcard so you would have access.
Also before you jump ship make sure you check into your next phone for the possibilities of syncing past event not sure if any phone OS will do that. Worst case carry your old phone without service until you no longer need those events.
edit: just looked around and didn't find anything yet but you might want to look in third party calendars from the market maybe they have the ability to past those older events.