reduce queries for user preferences lookup - Jetspeed 2.1.2

Hi everyone, using Jetspeed 2.1.2 (we know we should upgrade ASAP!) we 
are experiencing some performance issues in loading and rendering psml 
pages due to many queries like these:

SELECT 
A0.NODE_ID,A0.PARENT_NODE_ID,A0.NODE_NAME,A0.NODE_TYPE,A0.FULL_PATH,A0.CREATION_DATE,A0.MODIFIED_DATE 

FROM PREFS_NODE A0
WHERE (A0.FULL_PATH = '/portlet_entity/<fragid>/anon') AND A0.NODE_TYPE = 0
;

SELECT 
A0.PROPERTY_VALUE_ID,A0.NODE_ID,A0.PROPERTY_NAME,A0.PROPERTY_VALUE,A0.CREATION_DATE,A0.MODIFIED_DATE 

FROM PREFS_PROPERTY_VALUE A0
WHERE A0.NODE_ID = <nodeid>
;

These two tables are growing big, there are many users registered in the 
portal (about 6000), and the number of nodes and properties is high:
PREFS_PROPERTY_VALUE ~ 150.000 records
PREFS_NODE ~ 600.000 records

It seems that Jetspeed, for every fragment, is looking for user 
preferences and properties.
Is there a way to avoid these queries?
All of our fragments have readonly preferences; can we stop Jetspeed 
looking for prefs using the attribute readOnly="true" in preference tag 
of fragments?

Our Jetspeed installation is in a Linux Ubuntu 64bit server and a MySql 
5.1 database server.

Thank you for your support!

ROb