Currently for ripped movies I run through Subler as an easy way to add things.
Subler does the job too. If you are good with that, you don't need MetaZ or MetaX or similar. The main idea is being confident you tagged them outside of iTunes if you want to do the "delete-move-import" solution. Nothing very painful can happen either way but if the metatags are NOT in the files, you'll have some missing bits of file information when you re-import them again (so it's just a bit more work to bring them back to as they are now).
And I too tagged all of my home movies with individual posters and made them "TV Shows" so that they would organize by year. That was great in

TV1 but is broken in

TV3 (they still organize by year but share one poster for all files within any given year). I hate it when Apple takes away good features like full "show" tag support (in "Movies" too) and things like individual posters for each media file.
----------
I began using ATV2 then ATV3 Presets,and was unhappy with the encoding time and file size. My times were nothing less than 11 hrs with most being anywhere from 15-18 hrs, with sizes ranging from 8-15gb. So, I started using the Normal Preset and I'm quite happy with the resolution, picture playback, file sizes and speed. Now, most of my Blu Rays will encode between 2.5hrs. to 5 hrs. with sizes between 2-6gb.
You are trading off a lot of fine detail when you do this. And you are trading off resolution when you use the

TV2 preset (about a million pixel difference between 720p and 1080p).
You might want to render a single chapter from 4 or 5 movies and then use "Normal" and maybe "High Profile" presets, 720p vs. 1080p. Then pull them into iTunes and push them through your

TV3 for some head-to-head testing. If you care about fine detail in the picture, it should show with such dramatic differences in file sizes. Be sure to find a chapter of dark (nighttime) material as at least one of your tests.
Nothing wrong with "Normal"... just pointing out that you are shifting a very long way from Blu Ray master to end result. If you mostly watch on smaller screens (like iPads or iPhones), the head-to-head probably won't show much to you. But on bigger screens- like a big 1080p HDTV- I bet you will see the differences.
As far as how long it was taking, that's directly tied to speed of your system. 15-18 hours suggests you could use newer hardware, especially if you are going to be processing 350 BDs. I have a 2010 iMac and the average conversion is about 2-3 hours. Even newer machines does it even faster than that. Based on those times, I would guess you have a 2005-7 laptop? If you have some spare cash, upgrade. For the task of converting 350BDs, you could really use some faster horses.