As an heavy user of session restore and tons of open tabs, I would be OK ignoring updates to tabs that have not been active for a while. For example, let's say

As an heavy user of session restore and tons of open tabs, I would be OK ignoring updates to tabs that have not been active for a while. For example, let's say I have 10 tabs open but I have been using only the latest tab during the last 5 minutes. In this scenario I don't care about the cookies (eg due to ongoing ajax) nor the state of the other 9 tabs. If the browser crashes I'm OK with those 9 tabs being restored with a 5 minutes old snapshot. So for instance FF should be smart to save the state of new/recent tabs, and should slow down progressively on old/inactive tabs.