15 tabs? I manage multiple projects, one per window, and have about 15 to 30 tabs per window. So maybe 300 tabs.
/s but I suppose I've developed a work flow that adapts to the RAM I've always had. I've seen people with zillions of tabs and I do wonder if it's really that much more productive than the occasional HTTP request to reopen one. I find leaving things open as a form of bookmarking clouds my mental space too much.
I do intend to have beastly RAM on my new desktop so who knows, maybe I'll be like you in a year.