Daniel,
The easiest way to resolve this is to disable Policy Validation in the Policy Manager during development.
If you are using the standalone Policy Manager client, it is located under "File" > "Preferences" and then uncheck "Policy Validation Feedback".
If using the web client, you can find it under "Manage" > "Preferences".
This will disable validation. You can always turn it back on whenever you want to validate.
Alternatively, validation time is affected exponentially by the number of decision points in a policy, if there are more than 40-50 decision points, validation may take an exceedingly long time, or appear to hang indefinitely. You can reduce the number of decision points by splitting up policy into different services that call each other as well. Apart from re-writing your policy to reduce the decision points, there aren't any ways to increase validation speed.
Regards,
Azad