Whether H1 can travel in the middle of pending extension with USCIS?

My spouse H1 is getting expired on Aug 9th 2019.his company will apply H1 extension in January 2019.
We need to travel to India in April 1st week . In this situation if he can apply H1 extension in Jan 2019

I strongly recommend to NOT travel while H1B extension is pending.

You can opt for premium processing and get the result before your travel but avoid travel at all costs while the application is pending.

Thanks for your fast response.
Please advise it is safe if he applies for H1 extension in May ,2018.
Normally what is the processing Time for H1 extension and how long he can working in USA once H1 gets expired

He can apply for extension before 6 months of expiry of existing H1B.

We track current processing times for H1B extension here (updated daily):