Gmail surely does use a lot of memory. So do the blocking addons. Does it use less in Chrome? The more mail displayed at once in a folder, the more memory used. Since i bumped it up to 100 per screen, the memory usage certainly increased. The "energy Impact" is also high, but chills way down once the tab is left alone for a bit. Honestly i have never left any browser open for days with heavy use, they seem to gag after a while. But then i never had a particularly good machine, either, so that may mean little. Had you tried simply closing the Mail and Calendar tabs occasionally, or killing their respective processes? It may be better than a restart if you have a lot of tabs open. Other browser windows are running their own parent process, so they shouldn't matter, really.