Saving & storing a few urls in a Session isn't the issue. Sessions are just a nice way of saving things you are working on. Such as when you are researching a subject or issue & have 10 tabs open but need to go to work or bed. Then you just save those open tabs to a new session so you can open that Session again later. Sessions have no other purpose than that.
Opera 12 like Firfox & IE can handle massive amounts of bookmarks without any problems at all. They do so because bookmarks are simple a saved url. I have never tried but imagine in Opera 12, Firefox & IE, one could have 1 million or more bookmarks without it causing any problems. Bookmarks are little more than a text file, each line being a single url.
Opera 21 or any version of Opera after Opera 12 can't handle bookmarks. Opera doesn't want their web browser to handle bookmarks anymore & I told you why "Profits".
Opera is making a great deal of money by forcing thier users to use search engines to reach websites. It's all about big data, getting people to rely on others rather than themselves. Everyone today is using search engines, linking all their social networking sites, having someone else remember their login credentials.
Some of us are not interested in sharing our lives with the Googles of the world, we prefer anonimity. My personal privacy is critically important to me, I don't link anything, I don't have anyone else remember my login credentials.
Funny thing is IE is the most anonymous browser. When I install Opera, Firefox & Chrome I have to spend hours running wireshark & netcat to capture all the IP addresses those browsers are "phoning home to" IE doesn't do that but the others all do. After installing Firefox a week ago I ended up adding over 200 IP addresses to my host file, to block my Internet connection from contacting those IP addresses. Those are IP addresses Firefox tries to connect to just by opening the program & without ever connecting to a website. Opera & Chrome do the same thing. Not just when you start the web browsers, even while surfing from website to website those browers are still phoning home.
But you wouldn't know anything about that because you are just a user. Who like most everyone else is oblivous to just how much tracking & monitoring of our surfing habits are taking place & by who. And I won't even tell you about extensions, addons & those toolbars people keep installing on their computers & cell phones.
Before you say I am being paranoid get yourself Wireshark & run it, see for yourself. Start Wireshark then open Opera without connecting to any websites & watch how many IP adresses Opera connects to before you ever do anything. Then if you want to do something about you need to learn how to use your host file, mine is blocking my computer from connecting to over 18,000 IP addresses. The host file is actually the only way to block connections to & from your computer. Web browser addons & adblocking software only block the display of ads, the connections to & from your computer still take place!