[zie]

Picture proof of memory usage: http://imgur.com/a/7RgZt

FF 1.3GB memory with 10 tabs and 5% of CPU, with FF in the background.

Switching tabs is absolutely not instant, opening new tabs is reasonable, bet definitely not instant.

I'd love your numbers ;)

[SAI_Peregrinus]

I'm in a similar situation to the GP. Addons used to help:

BarTab Heavy - Allows unloading of unused tabs. Lets tabs act like temporary bookmarks. Tree Style Tab - Just great tab management. uBlock Origin + uMatrix - Lots less cruft loaded and running to slow things down. Session Manager - Lets me save windows with groups of tabs like bookmarks, works amazingly for looking things up and being able to restore a lot of references at once.

[kpcyrd]

Well, one of those tabs is graylog and one is gmail. Do you have e10s enabled? (open about:support, check for "Multiprocess Windows")

[AstralStorm]

This only works properly since 50+ version. You will get many issues if you try it in the old one.