Using single process Firefox forks I often load in 500 tabs plus another 500+ suspended in under 4 GB. Of course I'm also running NoScript temp whitelist only and most sites are websites not web applications. But 1000 loaded tabs is certainly doable in way less than 16GB of ram if you don't use a multi-process browser. It's just a shame this is written as a chrome style extension (which modern FF supports) and not a firefox extension.