The validity of an Egyptian tourist visa is three months from the date of issue. If it is not used before the time limit expires, it will expire and a new eVisa will be required.
The visa will be valid for another 30 days within Egypt from the date of entry if you fly within this 3-month timeframe.
The multiple-entry tourist visa, on the other hand, allows for stays of up to 30 days and can be used over a six-month span after the initial entry.