Firefox takes up too much system resources with multiple tabs open, there have been addons like RAMBack, Clusters, and TooManyTabs promising to take care of this but none of the above were practical to use and therefore did not remained on my computer after few days usage, however new addon BarTab is a perfect practical solution to the problem which works amazingly and I am definitely going to keep it - what BarTab does that it prevents loading tabs until needed saving system resources. Whenever you start Firefox instead of loading all the tabs BarTab puts all the tabs on your bartab and loads them only when you click on them.

Since there is no extra tab-bar this is very practical to use providing EXCEPTIONALLY good results, my Firefox memory resources usage went down from 241 MB to just 82 MB that's an amazing 290% improvement.