This limit is in place due to performance reasons and can't be removed from core searches. However, generally when users want more than 500 results it is because they are performing reporting tasks versus standard searching/navigation tasks. For those reporting tasks we have released ready reports. Ready reports offers the same features as searching plus you can adjust the 500 limit and execute saved contextual criteria. You can also calm the performance concern by setting up the ready reports app to use a reporting db If nessesary.
Ready Reports is extremely easy to install. You can learn more about it by watching the overview video on the collaboration site. You can also read the guide that is inside the extensibility pack.
There is a config in CustomerSettings.config
<add key="GSM.GlobalSuccession.MaxGlobalSuccessionSpes" value="500"/>
We don't recommend going beyond 500 and can't guarantee the system will perform. As with everything there is always an upper limit, so you may end up hitting it and having to do the replacement with db scripts. Can you run a query and see how many total specs are affected? For example, if its 550 you could push it, but if its in the 1000's you'll probably have to come up with a more technical hands on approach.