when my macbook dies because the battery needs to be recharged, how long until my tabs i had up before it died disappear?
when my macbook dies, will the tabs i had up before it died still be there?
They may be - although if not, you can select Safari - History - Reopen All Windows from Last Session...
(assuming that you mean Safari tabs).
Note that form data, or a site that required you to be signed in (like these forums), may not reopen exactly as before, losing some information... google searches where you changed search words may also be different.