Found this tip from TLCC which is worth trying if you have the memory to spare. The detail of the tip is here
In essence this is the tip
Want to reduce the time to start your Notes and Designer clients and get better overall performance? You can with a few configuration tweaks described below.Notes and Domino Designer run in Eclipse, a Java-based application. There are two settings in the jvm.properties file that you can change to increase the initial memory assigned to the Eclipse environment and to set the maximum memory used by Eclipse. These settings are listed and described below:vmarg.Xmx=-Xmx256m– This setting represents the maximum amount of memory (in MB) used by the Eclipse client. This setting can be increased from the default 256MB, however, never set this to more than 1024 MB. For my systems, I have this set to 512m and find I don’t reach that limit too often (more on monitoring memory usage later in this tip). If you have a machine with limited memory then be more conservative with these settings. If you have 2GB or more of memory then you can increase this setting to 768m or 1024m depending on what other applications you may also be running when you use Notes/Designer.
vmarg.Xms=-Xms48m– This setting represents the amount of memory (in MB) assigned when Notes/Designer first starts up. The default is 48MB, and this should be increased to at least 256 MB. This will improve the initial load time of the Notes/Designer clients as well as overall performance once they are started. Never specify a value for this setting to be more than the first setting (maximum memory that can be assigned).These two settings should be set in multiples of 16, such as: 128m, 512m, 768m, etc.
But take a look at the simple steps on the link to see how to do it for your client