Add "Open pinned tabs" checkbox option to the settings under general->startup section. Now it's available only in Config. I don't need to open all my pinned tabs at once and and fill the RAM by default.
The main reason to me for not taking advantage of pinned tabs is precisely the slowing of the startup process and the consumption of RAM when not needed...
Pinned tabs should only load on-demand, activated by use (and, as with any tab, should be able to be unloaded with something like right-click: Unload).