knowing Multi threading issues for FOP 1.1

Hi,
I am a software engineer - java/j2ee

We have a production application that creates 500 thousand pdf/day and it has implemented fop 0.95 As per current implementation in our code, we have not shared the FopFactory instance for threads. For each thread, we create a new FopFactory instance, so after 6 or 7 days, the application CPU usage is too high and the application needs to be restarted every 6 - 7 days.

As we know that creating new FopFactory instance for each thread is a very costly operation, so to cater to above problem can we share one FopFactory instance for all threads. Are there any problems reported with this approach in fop 1.1 because we can for sure upgrade to fop 1.1 from fop 0.95