Alan, congratulations! Well deserved. Since you purchased one of our bundles, I have access to your account and was able to took take a deeper look at your overall recent history to validate this.
First, your HM was beautifully paced. A negative split by 1%, practically perfect. You set yourself up for a PB with that discipline.
Looking at this and other past data, I would for sure drop to a 4:10 threshold now. The time until your next race is not relevant. If you identify a new threshold, use it right away (whether slower or faster).