iCal allows 25,000 events on iCloud. How do I get more?
Why not take the last 9 years of calendar entries, export them as an iCal Archive, then create a new calendar, import those entries, but do not sync to iCal. You can then delete those entries from your daily calendar, while maintaining history in your archive calendar. You can sync this archive calendar to your iPhone via iTunes, rather than iCloud. Of course, you can do this with your 10 years of entries as well, but you will not get the nice benefits from iCloud on your daily calendar.