Time limit to appeal.

I have approx 10 days in which to do my mandatory reconsideration. I am waiting on a consultant letter whom has offered his services. Christmas has not helped.
Jan 24 I will be going away to NZ for 5 weeks to see a relative whom has a terminal illness.
My MR will have been received by DWP by then but doubt I will know it’s answer, until my return. . I don’t want to involve people opening my mail.
In this instance, will I have enough time on my return (March) to appeal if it’s the worst case scenario, or do I need to be honest with them prior to going and be allowed extra time?
Thank you in advance.