You can only charge your time to the estate if the will allows you to charge your time to the estate. Usually, the only provision (and that is not always in) is for professional executors, solicitors and accountants to charge their time.
If it doesnt mention solicitors charging they can charge if instructed by executors
If the will doesn’t mention it, then I am afraid that your time is given for nothing.
I’m sorry if the answer is unfavourable for you.
Can I clarify anything for you?