Whens the last time you let windows sit at thelogin screen for a few hours so trim and garbage collection can do their things?
Never, I built my computer half a month ago. I did TRIM myself by going into optimization, should I leave my computer on at night?
The TRIM command tends to go into action every time a part of the drive is overwritten. So, that'd be upon startup (as the OS loads/modifies system files), when you empty recycle bin, when you download or create a new file, etc.. That said, it is still up to the drive controller to execute the actual garbage collection which, sometimes, takes time. There's no need to keep your computer at a login screen, but since your SSD model does idle-time garbage collection, you could give it extra idle time to let the drive's controller do its thing (e.g. leaving the machine on, doing nothing or little - browsing/). Disabling hard disk sleep is a good idea too, since SSDs don't go into "sleep" mode anyway.
As for why the SSD is slower than advertised, those advertised numbers show peak
performance (i.e. absolute maximum a drive can achieve, when it's new and empty). Real-life usage speeds will undoubtedly differ. I wouldn't worry about it, as those numbers aren't too far from those under peak conditions.