btw: laptop_mode is not a on/off switch but a timeout to delay writeouts after the disk got waken up (and some more). For flash based devices it makes sense to increase this value (YMMV) to pile up writes and put less write wear on the flash chip.

Since seeking on flash is fast it makes also sense to increas vfs_cache_pressure to 200, then the kernel prefers page cache over filesystem buffers (hint: on machines with a lot of ram try 1 there (but not 0!)) that gives insanely fast disk access.