You probably already noticed that some webdesigners like to set cookies expiration times to 100 years or more.
I have some cookies that are set to expire in 2040
A feature I miss from old Netscape and Mozilla Suite, is the option to set a max age for cookies.
My suggestion is that you can set a number of days, and any cookie older than that will be excluded.
For example, if you set the Max Age for cookies to be 30 days, it will mean that:
Any cookie that was set 30 days ago will be excluded.
That includes login cookies, so, in practice, you will have to reenter your password every 30 days for sites you frequently visit. (Which could be set exceptions)
Sites that you don't visit, the cookie will simply get deleted.